Lay down a piece of painter's plastic at the base of the wall to protect the floor surface from paint.
Inspect the bare wall for holes, cracks or dents. Check the trim work around the wall or windows in the wall to see if the gap between the trim and the wall has been caulked.
Caulk the seams by loading a tube of caulk into a caulking gun, cutting the tip off with a utility knife and then squeezing the trigger as you slide the tip across the seam. Smooth the bead of caulk out with the tip of your finger.
Fill all the holes or dents with drywall joint compound using a putty knife. Press the compound into the hole or dent with the flat edge of the knife blade and then smooth it out so that it's flush with the wall surface. Wait 24 hours for it to dry and then sand it smooth with a 120-grit sanding block. Dust the wall with a dust brush.
Pour a couple of inches of primer into a handheld paint holder, dip the paintbrush into the primer and paint a 4-inch border all the way around the the edges of the wall. Cut straight lines as you paint around the wall's perimeter. Cutting just means painting with a brush. Cut around any electrical outlets on the wall. Cut along the top edge of the baseboard trim, below the crown moulding trim and around any window trim. Paint out from these edges 4 inches.
Fill a paint tray with one-half gallon of primer and slip a half-inch roller cover nap onto the spindle of a paint roller frame. Screw an extension pole into the handle of the frame. Dip the roller in the paint tray paint until the nape fibers are loaded with paint. Roll the roller back and forth across the rolling area of the paint tray to roll off any dripping paint.
Walk to the left side of the wall and place the roller at the top of the wall just below the previously painted border. Roll paint all the way down to the bottom paint border just above the baseboard. Roll back up to the top and roll into the paint border near the ceiling or crown moulding. Roll back down along the corner of the wall overlapping the paint border by a couple of inches. Reload the roller with primer and repeat this process all the way across the wall. Overlap the primer boarder at the top and bottom of the wall by a couple of inches and overlap the previous roller lap by a couple of inches to roll out any roller lines.
Wait 24 hours for the primer to dry and then apply the finish coat of paint. Cut or paint the 4-inch boarder first and then roll the wall. Apply a second coat if needed, but wait 24 hours before doing so.