If the walls are not to bad than spackling is the easies thing to do. Simply scrape any loose plaster, paint off the walls. Then utilizing the existing wall as a guide spread a thin coat of spackle over the area. Use a small amount just covering the cracks and flaws. Spackling only becomes difficult if you have large deep holes to cover and there is no existing surface to use as a guide.
Do this a couple of times until you are satisfied with the appearence.
One thing to be aware of is that you don't want to spend too much time playing with the spackle. Simply wipe it on let it dry and then smooth with sand paper.
After sanding prime with a good quality primer like Kilz and then paint to match.