There are some red flags that can increase your chance of an unwanted meeting with the IRS.
Many tax returns are run through a computer selection process that assigns a value to certain key items on your return. If the total score exceeds the guideline set by the IRS, the computer will kick out your return for further examination to determine if it should be audited.
If the IRS discovers a possible error, it sends you a letter explaining the apparent mistake. The letter also includes the proposed correction and notes any tax owed plus interest and penalties, if applicable. Most such letters don't require a visit to an IRS office.
Yahoo! Finance, H&R Block and Jackson Hewitt Tax Service, all provide valuable tax information.
If your tax return is complicated, hire a pro. If you do it yourself, always check the math — it will keep the IRS computer happy and make your life a lot easier.