Painting is a relatively straight-forward process: Pick out a color, get a few rollers and pans, clean the wall and you're good to go. Though some of us miss the mark with the specific hue (like that "cherry red" which turned out to be "blood burgundy"), the biggest mistake most will make is in calculating how much paint to buy. If you don't buy enough, you risk the chance of a mismatch. If you buy too much, the extra cans will take up space in your garage or closet for all of eternity. Thankfully, this video from Martha Stewart, while a bit on the promotional side, has the exact info you need to make the right decision.