Before beginning to paint, "cut in" around any corners or trim. To do this, load a small amount of paint on the end of the brush, press the brush against the wall so that it comes to an angle and gradually work toward the trim. Be careful not to get paint on the trim or any other surface. Work your way around all the trim and corners.
Painting pads can help when cutting around trim. The pads come with small wheels that allow you to paint up to the edge of the trim without getting paint on the trim. To use one, dip the pad face into the paint, being careful not to get paint on the rollers. Start painting near the trim, and work closer until the rollers touch it. After painting, go back and feather the edges of the painted area.
After cutting in around the trim, begin rolling the paint onto the walls or ceiling. When painting with a roller, paint in 3' by 3' sections. Paint in long strokes, using a zigzag pattern to achieve a more even coating. Start in an unpainted area, and work your way into a painted area. After applying the paint, go back over the freshly painted area to help ensure an even coating. As each section is finished, feather the edges by pulling the roller straight down and then lightly pulling it away from the wall as you reach the bottom of the freshly painted area. This will help eliminate roller marks on the wall.
To help save time in the painting project, consider a power roller. It holds paint in a reservoir and sends it directly to the roller, eliminating the need for paint trays. Cleanup is also easier.
Any painting project should begin at the highest area to be painted. For example, when painting both ceiling and walls, start with the ceiling.
Before painting the trim, fill in any nail holes with wood filler. Dab some filler material on your finger and rub it into the holes. After the filler has dried, sand it smooth.
To prevent getting paint on walls or floors, use a trim guard or a paint guard. A tape knife, which has a wide flat blade, also works well. Hold the edge of the blade tightly between the wall and the trim and paint the trim all the way up to the edge. Be sure to clean the edge of the paint guard frequently. Always paint baseboards last because of the possibility of bumping into them with ladders or dripping paint onto them.