As in all the other emergency scenarios we've gone through so far, it's important to remain calm when the earth starts a-shakin'. If you're indoors, get away from windows, drop under a sturdy table, desk or other protective area and cover your head with a pillow. Failing that, go to an interior wall in the house and protect your head with a pillow.
If you're outside, move to an open area that's away from buildings, power lines and other potential hazards that could be knocked down during an earthquake. If you're driving, get your vehicle out of traffic and park it somewhere that's also clear of trees, signs, traffic signals and light posts if possible [sources: CDEMA, California Department of Conservation].
Whatever you do, just don't run. Most earthquake injuries occur when people are hit by falling objects while trying to enter or exit a building.