<?xml version="1.0" encoding="us-ascii"?><InstanceReport xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"><Version>2.4.0.8</Version><ReportLongName>0008 - Disclosure - 2. Summary of Significant Accounting Policies</ReportLongName><DisplayLabelColumn>true</DisplayLabelColumn><ShowElementNames>false</ShowElementNames><RoundingOption /><HasEmbeddedReports>false</HasEmbeddedReports><Columns><Column FlagID="0"><Id>1</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><CurrencyCode /><FootnoteIndexer /><hasSegments>false</hasSegments><hasScenarios>false</hasScenarios><MCU><KeyName /><CurrencySymbol /><contextRef><ContextID>From2011-07-01to2012-06-30</ContextID><EntitySchema>http://www.sec.gov/CIK</EntitySchema><EntityValue>0001020477</EntityValue><PeriodDisplayName /><PeriodType>duration</PeriodType><PeriodStartDate>2011-07-01T00:00:00</PeriodStartDate><PeriodEndDate>2012-06-30T00:00:00</PeriodEndDate><Segments /><Scenarios /></contextRef><UPS /><CurrencyCode /><OriginalCurrencyCode /></MCU><CurrencySymbol /><Labels><Label Key="CalendarSupplement" Id="0" Label="12 Months Ended" /><Label Key="Calendar" Id="1" Label="Jun. 30, 2012" /></Labels></Column></Columns><Rows><Row FlagID="0"><Id>1</Id><IsAbstractGroupTitle>true</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>1</Level><ElementName>us-gaap_AccountingPoliciesAbstract</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText /><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>xbrli:stringItemType</ElementDataType><SimpleDataType>string</SimpleDataType><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>Accounting Policies [Abstract]</Label></Row><Row FlagID="0"><Id>2</Id><IsAbstractGroupTitle>false</IsAbstractGroupTitle><LabelSeparator>

</LabelSeparator><Level>2</Level><ElementName>us-gaap_BasisOfPresentationAndSignificantAccountingPoliciesTextBlock</ElementName><ElementPrefix>us-gaap_</ElementPrefix><IsBaseElement>true</IsBaseElement><BalanceType>na</BalanceType><PeriodType>duration</PeriodType><IsReportTitle>false</IsReportTitle><IsSegmentTitle>false</IsSegmentTitle><IsCalendarTitle>false</IsCalendarTitle><IsEquityPrevioslyReportedAsRow>false</IsEquityPrevioslyReportedAsRow><IsEquityAdjustmentRow>false</IsEquityAdjustmentRow><IsBeginningBalance>false</IsBeginningBalance><IsEndingBalance>false</IsEndingBalance><IsReverseSign>false</IsReverseSign><FootnoteIndexer /><Cells><Cell FlagID="0" ContextID="From2011-07-01to2012-06-30" UnitID=""><Id>1</Id><IsNumeric>false</IsNumeric><IsRatio>false</IsRatio><DisplayZeroAsNone>false</DisplayZeroAsNone><NumericAmount>0</NumericAmount><RoundedNumericAmount>0</RoundedNumericAmount><NonNumbericText>&lt;p style="margin: 0pt"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Consolidated Financial Statements&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The accompanying consolidated financial statements include
all of the accounts of the Company and its wholly owned subsidiary, Rotate Black, OK, LLC. (OKL).&amp;#160;&amp;#160;In addition, at June
30, 2012, the Company has included the financial statements of RBMS in the accompanying consolidated financial statements. (Note
7).&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Investments in 50% or less owned entities without controlling
influence by the Company are accounted for using the equity method. Under the equity method, the Company recognizes its ownership
share of the income and losses of the equity entity. Through June 30, 2011, the Company recognized an equity interest in RBMS.
(Note 7).&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;All significant intercompany accounts and transactions have
been eliminated.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Estimates&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The preparation of financial statements in conformity with
accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect
the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial
statements and revenues and expenses during the reporting period. Accordingly, actual results could differ from those estimates.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Financial Instruments&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The Company considers the carrying amounts of financial instruments,
including cash, accounts payable and accrued expenses to approximate their fair values because of their relatively short maturities.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Property and Equipment&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Property and equipment are recorded at cost and depreciated
over their estimated useful lives using the straight-line method.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Maintenance and repairs are charged to operating expenses
as they are incurred. Improvements and betterments, which extend the lives of the assets, are capitalized. The cost and accumulated
depreciation of assets retired or otherwise disposed of are relieved from the appropriate accounts and any profit or loss on the
sale or disposition of such assets is credited or charged to income.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Revenue Recognition&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Revenue is recognized when evidence of an arrangement exists,
pricing is fixed and determinable, collection is reasonably assured and delivery or performance of service has occurred. Management
fees earned under contract to operate and manage casino projects are recognized pursuant to terms of the agreement.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Intra-entity transactions for revenue and expenses earned
in connection with an equity investment are eliminated in accordance with guidance in ASC 323-10-35-5.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Share-Based Compensation&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The Company recognizes compensation expense for all share-based
payment awards made to employees, directors and others based on the estimated fair values on the date of the grant. Common stock
equivalents are valued using the Black-Scholes Option-Pricing Model using the market price of our common stock on the date of valuation,
an expected dividend yield of zero, the remaining period or maturity date of the common stock equivalent and the expected volatility
of our common stock.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The Company determines the fair value of the share-based compensation
awards granted as either the fair value of the consideration received or the fair value of the equity instruments issued, whichever
is more reliably measureable. If the fair value of the equity instruments issued is used, it is measured using the stock price
and other measurement assumptions as of the earlier of either the date at which a commitment for performance to earn the equity
instrument is reached or the date the performance is complete.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;The Company recognizes compensation expense for stock awards
with service conditions on a straight-line basis over the requisite service period, which is included in operations.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Basic and Diluted Net Income (Loss) per Common Share&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Basic net income (loss) per share (EPS) is calculated by dividing
net income (loss) available to common stockholders (numerator) by the weighted-average number of common shares outstanding during
each period (denominator). Diluted loss per share gives effect to all dilutive common shares outstanding using the treasury stock
method and convertible preferred stock using the if-converted method.&amp;#160;&amp;#160;In computing diluted EPS, the average stock price
for the period is used in determining the number of shares assumed to be purchased from the exercise of stock options or warrants.&amp;#160;&amp;#160;Although
there were common stock equivalents outstanding as of June 30, 2012 and June 30, 2011, they were not included in the calculation
of earnings per shares because their inclusion would have been considered anti-dilutive.&amp;#160;&amp;#160;As of June 30, 2012 and June
30, 2011, there were 3,900,000 and 2,021,333, respectively, total common stock equivalents.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Leases&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;Rent expense is recognized on the straight-line basis over
the term of the lease.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&lt;b&gt;Recent Accounting Pronouncements&lt;/b&gt;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;In February 2013, The Financial Accounting Standards Board
Issued FASB ASU 2013-02 Comprehensive Income (Topic 220) Reporting of Amounts reclassified Out of Accumulated Other Comprehensive
Income.&amp;#160;&amp;#160;The amendments in this update seek to obtain that objective by requiring an entity to report the effect of significant
reclassifications out of accumulated other comprehensive income on the respective line items in net income if the amount being
reclassified is required under U.S. generally accepted accounting principles (GAAP) to be reclassified in its entirety to net income.&amp;#160;&amp;#160;For
other amounts that are note required under U.S. GAAP to be reclassified in their entirety to net income in the same reporting period,
an entity is required to cross reference other disclosures required under U.S. GAAP that provide additional detail about these
amounts.&amp;#160;&amp;#160;The amendment is effective prospectively for reporting periods beginning after December 15, 2012.&amp;#160;&amp;#160;For
non-public entities, the amendments are effective prospectively for reporting periods beginning December 15, 2013.&amp;#160;&amp;#160;Early
adoption is permitted.&amp;#160;&amp;#160;The adoption of this pronouncement is not anticipated to have a material impact on the Company&amp;#146;s
financial results or disclosures.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0"&gt;In July 2012, The Financial Accounting Standards Board Issued
FASB ASU 2012-02 Intangibles-Goodwill and other (Topic 350), Testing indefinite-Lived Intangible Assets and Impairment.&amp;#160;&amp;#160;The
FASB amended the standards for testing indefinite-lived intangible asset for impairment to guidance that is similar to the guidance
for goodwill impairment testing.&amp;#160;&amp;#160;An entity will have the option not to calculate annually the fair value of an indefinite-lived
intangible asset if an entity determines that it is more likely then not that the asset is impaired.&amp;#160;&amp;#160;The objective of
the amendment is to reduce the cost and complexity of performing impairment and to improve consistency in the impairment testing
guidance among long lived asset categories. These amended standards are to be applied for fiscal years beginning after September
15, 2012, including interim periods with early adoption permitted.&amp;#160;&amp;#160;The adoption of this pronouncement is not anticipated
to have a material impact on the Company&amp;#146;s financial results or disclosures.&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-indent: 0.5in"&gt;&amp;#160;&lt;/p&gt;

&lt;p style="font: 8pt/normal Times New Roman, Times, Serif; margin: 0; text-align: justify"&gt;Management does not believe that any
other recently issued, but not yet effective accounting pronouncements, if adopted, would have a material effect on the accompanying
consolidated financial statements.&lt;/p&gt;



&lt;p style="margin: 0pt"&gt;&lt;/p&gt;</NonNumbericText><FootnoteIndexer /><CurrencyCode /><CurrencySymbol /><IsIndependantCurrency>false</IsIndependantCurrency><ShowCurrencySymbol>false</ShowCurrencySymbol><DisplayDateInUSFormat>false</DisplayDateInUSFormat></Cell></Cells><ElementDataType>nonnum:textBlockItemType</ElementDataType><SimpleDataType>na</SimpleDataType><ElementDefenition>The entire disclosure for the basis of presentation and significant accounting policies concepts. Basis of presentation describes the underlying basis used to prepare the financial statements (for example, US Generally Accepted Accounting Principles, Other Comprehensive Basis of Accounting, IFRS).  Accounting policies describe all significant accounting policies of the reporting entity.</ElementDefenition><ElementReferences>No definition available.</ElementReferences><IsTotalLabel>false</IsTotalLabel><UnitID>0</UnitID><Label>2. Summary of Significant Accounting Policies</Label></Row></Rows><Footnotes /><IsEquityReport>false</IsEquityReport><ReportName>2. Summary of Significant Accounting Policies</ReportName><MonetaryRoundingLevel>UnKnown</MonetaryRoundingLevel><SharesRoundingLevel>UnKnown</SharesRoundingLevel><PerShareRoundingLevel>UnKnown</PerShareRoundingLevel><ExchangeRateRoundingLevel>UnKnown</ExchangeRateRoundingLevel><HasCustomUnits>true</HasCustomUnits><IsEmbedReport>false</IsEmbedReport><IsMultiCurrency>false</IsMultiCurrency><ReportType>Sheet</ReportType><RoleURI>http://rotateblack.com/role/SummaryOfSignificantAccountingPolicies</RoleURI><NumberOfCols>1</NumberOfCols><NumberOfRows>2</NumberOfRows></InstanceReport>
