Paint finishes come in three general categories: flat (or matte), low-luster (eggshell and satin) and gloss (or semigloss). Choosing between them is simply a matter of weighing your room conditions, need for durability, and personal taste.
Flat — This gives most forgiving finish with the best color payout. If you want a saturated, velvety wall, a flat finish will give you rich results. If your wall has imperfections like uneven texture, patches or joints, flat paint will absorb light and make them less noticeable. However, flat finishes are not very durable and need to be carefully cleaned. Scrubbing flat paint could wear down the finish and cause sheen to appear in patchy spots.
• Best places to use flat paint: Ceilings (which tend to have flaws), accent walls, low-traffic rooms that don't need frequent cleaning.
Low-Luster — Many consider eggshell or satin finishes to be the best compromise between pigment and strength. These finishes look matte from straight on, but viewed at an angle, they have a subtle sheen. This makes them longer-lasting, but the sheen does show imperfections, especially if your room gets direct sun, so prepping the wall and using a good primer is still necessary.
• Best places to use low-luster: Living room, bedroom, dining room.
Gloss/Semigloss — The most durable finish, it holds up well in humidity and is easy to clean, but it does reflect light, calling attention to any and all minor flaws. In order for it to look smooth and even, the surface must be perfectly prepped and the paint applied very carefully to avoid streaky, uneven sheen.
• Best places to use gloss: Bathroom, kitchen, mud room, doors, baseboards.
(Image: Flickr user marie-II, licensed under Creative Commons)