Vast tracts of spackled wall, or a slick, shiny base paint, require priming. Primer is a slightly tougher version of paint, basically, and the kind you'll need depends on: (a) what you're painting over and, (b) what with. Ask at a paint store and they'll help you determine what the proper primer will be for your project.

4. Taping and tarping
Cheaper masking tape tends to have too much stick to it, and will pull (old and new) paint off. Meanwhile, proper painter's tape costs 4 times as much (still not a lot, but it's the principle of the matter.) Get some of both, using the good stuff for right-next-to-the-paint work and the cheap stuff for grunt work (taping down newspapers, additional protection to clean walls, holding paint tray liners in place, replacing video tape labels). Flaws in the line between fancy colored paint and white walls will torment you if you're not careful in this stage. Tape the edge of the wall carefully, making sure the tape edge is even where it overlaps.

Cover the floor with newspapers and tape them down, section by section. Don't use sheets (they absorb paint too readily, staining the floor) or trash bags (they don't absorb paint at all, which means you'll inevitably step in dripped paint and track it everywhere). Pull off all fixtures that are screwed on (like outlet plates), and tape over everything else. Tape along the edges of the wall plus two inches or so. Tape absolutely everything you don't want painted, and then some. This takes time. If you start getting bored and are doing a half-assed job, stop and come back to it. You'll thank me.

Okay! Now you're ready to …

5. Buy your paint!
If you're keeping the project small, odds are a quart of paint will be plenty. (For those of you who forget liquid measurements from 8th grade science, 1 quart=1/4 gallon). If this is a big job you're starting, paint a middle section of the wall, maybe 1-2 feet square, and leave it. Live with it a few days. Imagine the WHOLE WALL this color. If it works, continue. If not, start over.

Paint coverage is always an issue. On the can, they lie. They lie like dogs. Underestimating wall coverage is essential to ensure enough paint for touch-ups. Whatever numbers they state on the back of the can, figure it's actually 1/2-2/3 what they say. If in doubt, buy extra. It's far and away better to have a quarter-can left over than to find yourself in a situation where you have half a wall drying while you haul ass to buy more paint – which undoubtedly you'll discover, once you bring it back home, doesn't quite match the first batch. At which point you'll also have tracked paint in your car.