See my earlier post on this for a rundown of the qualifications, as well as some tips from the IRS.
Also consider buying a copy of your favorite tax software, or picking up paper copies. Because you'll have to provide some documentary proof of the purchase, you CANNOT e-file and claim the credit. (Though you can, if you wish, fill out the forms online, print them out, and send them in.)
For a good rundown of that and other potential pitfalls to avoid when claiming the credit, see The Wall Street Journal's MarketWatch advice.
