Remember to try and keep everything from floors to windows clean. The oven and other major appliances are essential and must also be kept clean. Skylights should be clear, too. And, do not forget to make bathrooms shine!

Try to eliminate any offensive odors. They're the first thing buyers notice, and often a permanent turnoff.

Eliminate Clutter; 

Which means, if you are not using it daily; keep it in a drawer or out of site.

Put away small kitchen appliances and other items that are sitting on countertops and tables, as sometimes they appear to make kitchens seem smaller with less cooking space.

Many people suggest removing photographs from table-tops, however pictures add friendliness, so just try to keep them to a minimum on shelves and table tops.

Organize the closets, it gives the appearance of tidiness, and if little things are tidy, everything is usually kept orderly.
 
If there's not a reason to leave something sitting around--remove it!

Outside Tasks;

Buyers nearly always comment if gutters are full of leaves and it makes them question other maintenance issues. So keep this in mind.

Store or organize items that make the yard look messy.  No yard tools or unnecessary items against the house or lying in the yard.

Lastly, make your front entry inviting. Decorate it, paint the door or buy a new door. It's the first and most of the time lasting impression of your home.