Using the best paint a brand offers will make painting a white ceiling easier and improve coverage over the cheaper alternatives. It can take as many as four or more coats of some low grade paints to cover completely, while quality paint will cover most surfaces with just one coat. The better paint will be a little more expensive but the labor saved will more than justify the extra cost. Most paint manufacturers offer a professional quality paint like this in their line of products.
Use flat latex paint for this job to minimize the chances of peeling and greatly improve the finished results over a shiny paint like semi-gloss. Flat latex is easy to touch up and repeated coats will not flash when the paint has dried. Shiny paints will show roller and brush marks, especially with repeated applications, and a shiny ceiling can be a distraction rather than an improvement.
If the walls are already painted skip this step, otherwise paint the walls of your room first. When brushing the wall color next to the ceiling, let it overlap a bit, but avoid getting big gobs on the ceiling as much as possible. If coverage is an issue, use two thin coats of paint rather than one thick one to limit buildup. This will create a crisper line between paint colors and minimize the color that must be covered with the white ceiling paint.
Let the wall paint dry for about a week before attempting to apply the masking tape. When you're ready, use painter's masking tape, at least 1 ½ inches wide. Apply short strips of tape to enable better control of the line and keep the tape as straight as possible. Tape around all the corners first.
And then do the straight runs, overlapping the ends of each piece of tape by an inch or so. To ensure a good bond, use a clean putty knife to press the tape to the wall. Push down lightly on the blade and pull it along, using lighter pressure on freshly painted walls to minimize peeling. Continue around the ceiling in this manner to finish taping the walls and then tape around any light fixtures or air ducts covers in the ceiling.
Use good quality white paint and brush a thin coat about three inches wide around the perimeter of the ceiling and any fixtures or vents. Use only a thin coat of paint along the edge of the tape to prevent bleeding underneath. If more coats are required to cover deep colors, let the first coat dry completely before applying another.
Pull the tape off the walls before the brush work can dry. Pull the tape slowly and at a sharp angle to minimize peeling. If necessary run the point of a putty knife along the tape to break any paint film that may prevent a clean break.
When the brush work is done, paint the remainder of the ceiling with a roller, without bumping it into the walls. Let the paint dry and check the finish for good coverage. If necessary, do another coat with the roller.