Cheap roller covers leave fuzz on the wall. Cheap brushes leave streaky brush marks. Avoid those multi-packs of rollers, ten for a dollar. Pay the extra few cents and get better tools. It'll be worth it. Honest it will.
2) Test for Loose Paint
Will the existing painted surface take new paint? And hold it for years to come? Test this out by adhering a strip of duct tape to the existing painted surface and...ripping it away. If flakes of paint more than microscopic size come off, you may need to scrape and sand.
3) Blue Tape
Also known as blue painters tape. This tape comes off easier and doesn't peel off primer or existing paint.
4) Wrap Brush or Roller
If you don't feel like cleaning your brush or roller at the end of the day and expect to get back to painting the next day wrap the utensils in a wet towel.
5) Painting Process
Paint in this order:
1. Ceiling 2. Walls 3. Trim 4. Cabinets 5. Doors