You may have noticed that when you log out or reboot Mac OS X Lion, you get a dialog window with a checkbox next to “Reopen windows when logging back in” that restores all of your currently open applications and windows.
If you don’t like it and you’re tired of unchecking the box to no longer reopen the windows, you can use a third party script to render the feature useless. To clarify, what this does is disable the feature completely on a constant basis, regardless of whether that checkbox to preserve windows is checked or not, the windows will not restore.
While this is part of OS X Lion’s Resume feature, this is different than disabling app Resume completely or on a per application basis, because this only effects reboots and logouts.
Get the full instructions here: Disable “Reopen Windows When Logging Back In” in Mac OS X Lion Completely | OSX Daily