Participating is a great way for your family or organization to be prepared to survive and recover quickly from big earthquakes.
PROTECT YOURSELF. SPREAD THE WORD.
DROP to the ground (before the earthquake drops you!),
Take COVER by getting under a sturdy desk or table, and
HOLD ON to it until the shaking stops.
If there isn’t a table or desk near you, drop to the ground in an inside corner of the building and cover your head and neck with your hands and arms. Do not try to run to another room just to get under a table.
These are general guidelines for most situations. Depending on where you are (in bed, driving, in a theater, etc.), you might take other actions, as described in Recommended Earthquake Safety Actions(PDF | RTF).
The main point is to immediately protect yourself as best as possible where you are. Earthquakes occur without any warning and may be so violent that you cannot run or crawl; you therefore will most likely be knocked to the ground where you happen to be. You will never know if the initial jolt will turn out to be start of the big one. You should Drop, Cover, and Hold On immediately!
What NOT to do:
DO NOT get in a doorway! In modern houses and buildings, doorways are no safer, and they do not protect you from flying or falling objects. Get under a table instead!
DO NOT run outside! Running outside is especially dangerous, as glass, bricks, or other building components may be falling. You are much safer to stay inside and get under a table.