Be afraid...be very afraid...

Be very careful who prepares your tax return
Stay away from any preparer who "guarantees" a refund, or who gets paid on the basis of how much you get back. Remember that what you get back is a function of how much you had estimated or withheld in the first place. The IRS has a hit list of preparers with a history of problems, and clients of these preparers are more likely to be audited.

Be afraid, very afraid, of any tax preparer who knows tax-planning techniques that no one else knows...

Steer clear of questionable shelters
Stay away from tax shelters that promise you deductions so large you actually "make money" on the tax savings. They are typically based on an over-valuation of assets on which the IRS can nail you in an audit. If a shelter seems too good to be real, it's probably not legitimate.