The April 15th filing deadline surprised you this year and you're wondering how to file an extension. What to do? You can go to the IRS website and download form 4868 (Application for Automatic Extension of Time To File U.S. Individual Income Tax Return) and mail it in. That's it.
There are several e-file methods that you can use and most will let you do the 1040 basic stuff for free but charge you to send in your state forms. All require you set up an account and fill out the basic information. Information easily transfers to other forms including the extension. You'll get a confirmation that your filing was sent and you should go back to the site you used to e-file and confirm that the IRS accepted it.
If you're in the state of California then you can get an automatic extension until Oct 15th, 2009 to send in your forms.
If you owe money, then you better pay by April 15th, because you're still required to pay up regardless of the extension. I'm not a tax professional so don't blame me because you waited to the last minute!