After I file my taxes, I generally worry about getting audited. When does the IRS notify you if you are going to be audited?

Generally speaking you will be notified of an audit between 12 and 18 months after you have filed your tax return.  The statute of limitation is 36 months from the time you have filed your return.  Keep in mind, there are no statute of limitation of you did not file a return. 

Note:  If you have understated your income by 25% or filed a fraudulent return then the 36 months is extended.  In the case of the understated income the extension is to 6 years.  In the case of a fraudulent return there is no limit, but generally the IRS won’t audit anyone after 6 years.  (NOLO Tax Savvy for Small Business, p 279)

Who must I send 1099s too?

I was challenged this week to answer this question.  I thought it was pretty straight forward at first but my answer started a controversy in the office.  My answer was directly from the IRS Publication called “2013 Instructions for Form 1099-MISC.”   
Which says, “Specific Instructions File Form 1099-MISC, Miscellaneous Income, for each person to whom you have paid during the year: At least $10 in royalties (see the instructions for box 2) or broker payments in lieu of dividends or tax-exempt interest (see the instructions for box 8); At least $600 in rents, services (including parts and materials), prizes and awards, other income payments, medical and health care payments, crop insurance proceeds, cash payments for fish (or other aquatic life) you purchase from anyone engaged in the trade or business of catching fish, or, generally, the cash paid from a notional principal contract to an individual, partnership, or estate; Any fishing boat proceeds; or Gross proceeds of $600 or more paid to an attorney. See Payments to attorneys, later. In addition, use Form 1099-MISC to report that you made direct sales of at least $5,000 of consumer products to a buyer for resale anywhere other than a permanent retail establishment. You must also file Form 1099-MISC for each person from whom you have withheld any federal income tax under the backup withholding rules regardless of the amount of the payment.  Trade or business reporting only. Report on Form 1099-MISC only when payments are made in the course of your trade or business. Personal payments are not reportable. You are engaged in a trade or business if you operate for gain or profit. However, nonprofit organizations are considered to be engaged in a trade or business and are subject to these reporting requirements. Other organizations subject to these reporting requirements include trusts of qualified pension or profit-sharing plans of employers, certain organizations exempt from tax under section 501(c) or (d), farmers' cooperatives that are exempt from tax under section 521, and widely held fixed investment trusts. Payments by federal, state, or local government agencies are also reportable. 
Exceptions. Some payments do not have to be reported on Form 1099-MISC, although they may be taxable to the recipient. Payments for which a Form 1099-MISC is not required include all of the following.  Generally, payments to a corporation. But see Reportable payments to corporations, later.  Payments for merchandise, telegrams, telephone, freight, storage, and similar items. Payments of rent to real estate agents. But the realestate agent must use Form 1099-MISC to report the rent paid over to the property owner. See Regulations section 1.6041-1(e)(5), Example 5, and the instructions for box 1.Wages paid to employees (report on Form W-2, Wage and Tax Statement).  Military differential wage payments made to employees while they are on active duty in the Armed Forces or other uniformed services (report on Form W-2).  Business travel allowances paid to employees (may be reportable on Form W-2).”  At issue was the question of do we need to send 1099 to companies like Office Depot or Walmart.  We spend over 600 per year with them so some in the office thought we did.  Professor Karl sent me some information confirming my belief that we do not need to send them 1099.   
Additionally, I came across a blog (http://www.indianabusinesslawblog.com/2010/11/how-will-the-upcoming-changes.html) that mentioned a new law that would require such action.  However, the article linked to an update that shows that the law was repealed and that the requirement does not exist.  (http://www.indianabusinesslawblog.com/2011/04/form-1099-reporting-changes-re.html).

When does the IRS notify you if you are going to be audited?

Generally speaking you will be notified of an audit between 12 and 18 months after you have filed your tax return.  The statute of limitation is 36 months from the time you have filed your return.  Keep in mind, there are no statute of limitation of you did not file a return. 

Note:  If you have understated your income by 25% or filed a fraudulent return then the 36 months is extended.  In the case of the understated income the extension is to 6 years.  In the case of a fraudulent return there is no limit, but generally the IRS won’t audit anyone after 6 years.  (NOLO Tax Savvy for Small Business, p 279)