Start painting a ceiling on the edges. Using a good-quality paint brush loaded with a good dose of paint, cut about two inches of paint in around the edges and corners of the ceiling. Then, switch to a roller.
Get a four or five foot extension pole for the roller. Starting at a corner, paint in sections about three feet square. As you paint each section, roll a W and a couple of X’s rather than trying to paint straight lines. This will leave a more even coat of paint on the ceiling.
Always overlap one stroke over the last one you rolled. This will ensure that you don’t miss any spots.