Take down window blinds, and remove switch-plates and outlets.
Move all furniture to the middle of the room and cover it with plastic.
Use tarps or plastic to cover floors as well.
Fix cracks and holes with latex caulk and drywall compound.
Apply two coats of paint. Wait till the paint is completely dry before applying the second coat.

Types of paint used.

Flat paint covers well all imperfections but most of the flat paints are non washable. The dirt will not come off the wall and you will need to touch up or repaint the area if it gets dirty. There are washable flat paints, but they are more expensive. Flat paints are usually used on the ceilings.
Low sheen does't hide the imperfections that well, but it is washable. Most of the interior walls are painted with low sheen. The higher the shine the easier it is for cleaning. Flat and low sheen paints are very easy to work with as you can apply this paint in any direction without leaving any brush or roller marks.
Eggshell, semi-gloss and gloss are harder to apply, as you always need to keep a “wet edge” in order not to leave any brush marks.Those are more expensive paints as well. They are mostly used to paint kitchens, bathrooms, trim,doors and baseboards.
The sheen may vary from one store to another. Paint that is called eggshell in the Home Depot and does not have a lot of sheen, will be with higher gloss if purchased at Dunn Edwards store. Equivalent to Home Depot's eggshell will be satin finish at Dunn Edwards store.