Here's the consolidated list of what to do: (1) Don't use the usual blue painter's tape for most surfaces. Use the purple 3M tape, or the green tape another poster recommended. (2) When using painter's tape on a wall that's been recently painted (ex: you have to paint trim on a wall you just painted, wait seven days for the paint to cure before using tape. Otherwise you'll just end up pulling the not-yet-cured paint off. (3) To avoid paint getting under the tape's edge, apply it carefully, use an orange stick or other firm yet pliable stick to rub the "live" edge down, and don't try to flex the tape or otherwise buckle it. (4) Do not leave the tape on for more than 8-12 hours. (5) Remove the tape while the paint you just applied is still wet. Do not wait for it to dry - you may pull paint away with the tape. (5a) If you waited too long and the paint dried, use a brand-spanking- new utility/razor knife blade to LIGHTLY score any place the paint has gone over the tape.