If painting walls or ceilings using a roller, do the corners first with a small paintbrush since it would be impossible to reach right into the corner with the roller. Start in one corner and coat the rest of the wall or ceiling with your roller, crisscrossing strokes lightly so as to leave no misses. Always make the first stroke in an upwards direction when painting walls so there would be less chance of excess paint oozing or dripping. Work with a slow, steady motion, and don't allow the roller to spin to avoid getting spattered with paint.
For painting narrow areas, there are inexpensive rollers available which measure just 3 inches in width. To reach all the way into corners when both surfaces would be painted in the same color, there are doughnut-shaped rollers, known as corner rollers. These eliminate the need for a brush in the corners. When using these type of rollers, you still paint corners first, then finish the larger areas with the regular roller.
Clean the roller cover at once after the job is done. It should take no more than a few minutes. Start by rolling out as much of the excess paint as possible, using old newspaper or scrape the cover to be rinsed in turpentine, mineral spirits or a similar solvent. Better still, use one of the special liquid cleaners which are sold for just this purpose can be used. These liquids can be used again and again, and they do a faster and more thorough job of flushing pigment out of the fibers.
After cleaning, wring out the surplus liquid by squeezing the fibers between your fingers. Wipe right away using a clean cloth, then wrap in sheet plastic or aluminum foil to keep the cover soft and ready for use the next time.