Inspect the wall for cracks in the stucco. Small cracks will be filled in with the paint but larger cracks will need to be filled with an elastomeric sealant.
Scrub the wall with soap and water to get rid of dust, dirt, mildew and loose paint.
Prepare the area for painting by removing fixtures, covering areas you don't want painted with masking tape and putting a drop cloth on the floor.
Select a paint. Acrylic latex paint formulated for stucco is the best choice. Be sure to use exterior paint for an exterior wall.
Fill up a roller pan with the paint.
Dip a paint roller into a roller pan full of paint and get it pretty saturated. If the roller is full of paint the paint will get into the rough surface of the stucco more easily.
Start from the top of the wall and roll down in a straight column. Then roll up. Next, shift a bit to the left or right and start a new column overlapping with the old one.
Go over your work to cover any missed spots as the paint starts to run out.
Load the roller with paint and start painting again.
Clean up when you're done.