Go beneath the staircase when the earthquake hits. Brace yourself against the wall and lower yourself to the ground.
Lower your head and protect your eyes with your arm, facing the wall beneath the stairs. This will also protect your head, while preventing stray debris or dust from kicking up and impairing your vision.
Remain beneath the staircase until the earth stops trembling. When it seems safe, check yourself for injuries before helping others. Be advised that aftershocks do occur, so vacate the building as soon as possible.