There are lots of things that are instantly rewarding, one is to paint a room. It can make a dramatic transformation very quickly. It can change the mood, as well as the energy in a room with very little cost and almost as little effort and give you a good return on your investment where buyers are concerned. Todays buyers want to do very little work even painting, so the more you can do to remove obstacles to your house selling the better. Avoid strong colors, and don't choose anything to anemic either, it can make a home look anti-septic.
Realty Times just published a great article, A Weekend Project: Newly painted walls. It does a great job laying out the process and what you actually need to do before you open that can of paint. Preparation, one of the things us guys often overlook.
It covers filling holes, sanding and even washing the walls down with a one part bleach to three parts water mix to kill off any mildew you might have, don't forget to wash the walls afterwards as well. Then move furniture, either out of the room or to the center of the room and cover it with drop cloths as well as the floor where you will be working. You may need to tape off areas where you don't want paint to go, I can assure you this takes time, but is well worth it.
If you have a particularly strong color on the wall now, you may need to use an undercoat to mask it completely, some companies offer undercoat and top coat in one, I have found it better where the paint is a really strong color to use separate products. Finally you can paint your final color, and it may still require a couple of coats. Paints today dry pretty quickly, so you should be able to knock this out over a weekend.
Ask at the store for help on selecting brushes and rollers, and if you have high walls an extension pole may be a good idea for reaching those high spots. Good luck and realize a freshly painted home looks better to buyers and keeps your home looking well maintained, and matching the look today's buyers want.