When rolling paint on a ceiling, maintain a wet edge at all times to avoid creating lines and ridges. If you're using fast-drying paint, you may have to work faster than you anticipated and without taking a break. Both speed and ease can be achieved by using an extension handle so you can paint from the floor instead of from a stepladder that has to be moved around the room. Many roller handles are made to accept a screw-in extension that you can buy at the paint store, but you may want to see if the threaded end of your broom or mop handle will work.
You probably won't have enough room to use the zigzag technique (see Painting Walls) over and under windows and above doors and doorways. Instead, just roll the paint on horizontally. For areas that are narrower than the standard 7- or 9-inch roller, use a 4-inch roller or a paintbrush. (The little roller is best because it will give you the same surface finish as the rest of the wall.) Brushes apply paint less evenly and tend to leave trails.