First, consider keeping your tax records in a safe place for at least three years. If you used desktop software to prepare your return, make sure you save a copy of the data file. If you used online software, you'll want to save a PDF-version of your tax return as well as a printout. Also save any confirmation emails regarding your e-file. This year I've had a handful of clients who filed their returns electronically last year, but the IRS claims never to have received them. Saving these confirmations can help prove you filed on time in case the data gets lost later on.
Secondly, you may also want to set up an organization system for next year. Even with all the various technical gadgets we have available, I'm still a fan of keeping things simple and easy. I really like the file folder idea presented in About.com's video on tax organization tips for freelancers. I would extend this concept to any taxpayer at all. Just look at the types of income and deductions on your tax return, and create folders to store receipts and statements related to that. The idea is to try to store the data you'll need next year in an easy-to-find location.
Third, consider revising your tax withholding. There's a fairly easy to use withholding calculator on the IRS Web site. To use this calculator, you'll need a fairly reasonable guess about your income and deductions for next year. The better your estimates, the more accurate the calculator can get your withholding to a level that's just right for you.