Windows: Replace torn or bent screens. If you cannot remove them entirely; better to have no screens than to have unsightly torn screens. If you have any cracked or broken panes make sure to replace them.
Doors: Check to see that all doors open and close freely, this includes closet doors and sliding glass doors. Oil any squeaky doors and remove or replace any broken doorstops. Make sure that the door hardware is tight and not lose, particularly doorknobs. It is also a good idea to inspect your kitchen and bathroom hardware.
Walls: One of the most beneficial things you can do in selling your home is to paint or touch up the interior. Out of all the things you can do to spruce up your home, none is more effective vs. the time and effort you will spend. Inspect your wallpaper, it should be clean and not have any edges pulling away from the wall.
Floors: Inspect your floors. Repair or replace missing or damaged pieces of tile; polish if needed. Pay particular attention to high traffic areas.
Carpet: Steam cleaning is the best answer for soiled carpets. If you own indoor pets you may want to clean your carpet some time before your home is placed on the market to insure that any pet odors have been eliminated.