How do you paint a ceiling?

I've been a painting contractor for 32 years. Here's how you do it: you're going to need two coats of paint at least. For the first coat, roll your paint parallel to the ceiling to within a couple of inches of the ceiling, then using an angle cut brush of 2 to 2 1/2 inches in width (spend some money and get a good brush; don't use a piece of crap) paint up to within 1/8 to 1/4 inch of the ceiling. I like moving from right to left and painting from left to right into the paint(always paint into the paint you've brushed on the wall, not away from it). When you come back to do your second coat it will be easier to cut a line right at the ceiling because your brush slips more smoothly over the fresh first coat. The difference in color between the wall and the ceiling will make it easier for your eye to tell your hand where to go with the paint. Unless there is a perfectly sharp corner at the ceiling your line will be either on the wall or on the ceiling. In general, it's better to get it more on the ceiling than on the wall, because otherwise, assuming the ceiling is lighter, the line of your new paint will look more uneven from a distance.