Professional painters will start by painting the ceilings first, then the walls, and finish up with the trim. Lou Manfredini, Ace's Home Expert, has some advice to help get the job done right.
How to Paint Walls and Ceilings
You'll want to make sure you're protecting the areas before you paint. Use painter's tape to tape off areas you do not want to get paint on.
The most professional way to start painting your ceiling is to use the cutting in technique. Use a 2" trim brush
to cut in a line along the edges. Make this line, roughly, 4" wide. After outlining your area, use a roller
in a zig-zag pattern to coat the rest of the ceiling. Do not over saturate your roller. This will l eave drips, marks, or streaks.
After you ceiling has dried, tape off
the ceiling to avoid painting over your recent work. Tape the door trim, wall trim. window trim, and any fixtures. Use the same cutting in technique as before. Once cutting is down, use the same rolling technique to finish off the walls.