Karyn, you would prep just like you normally do for painting. There will probably be nail holes and the like from pictures that were hung to patch. After the paper and glue is all off and any patching done and sanded, a coat of primer is in order. You can get the primer tinted to get close to the paint color you plan to use to make one coat paint coverage more of a possibility. I really prefer to use the primers that come from Zinnser or KILZ rather than the ones that the paint company suggests. The paint manufacturer wants you to use their primer, which may just be a watered down version of their paint. The specialty primer/sealers take care of more kinds of potential problems.