Paint the walls and ceiling both the same color. Use Kilz primer on the ceiling and then Kilz paint on both the walls and the ceiling. I have been in houses where the ceiling and walls were the same color and it actually made the rooms look very rich. I have always done two coats of paint, even when I used paints that said "one-coat coverage" - you don't end up with roller marks and it looks more professional, since this is what the professionals do. I have a friend who use to be a professional painter and he always did two coats no matter what color or brand of paint he used.