Take a minute to read through the full Repair vs. Capitalization Audit Techniques Guide found to the right. This is the most current version of the ATG available, and can be found on the IRS' website here. However, please keep in mind that this Audit Techniques Guide does not take the new regulations into account, as it was last revised in August of 2011.
Remember: Audit Technique Guides are not authoritative and should not be treated as tax law. However, they are the IRS's guidance to their examiners, and offer excellent insights to taxpayers and tax professionals alike on how best to prepare studies and reports.