Stay out of the yellow arc. Always wear your seatbelt snugly, and take a minute to secure anything loose in the cabin before entering rough air. As simple as they sound, these two precautions reduce the possibility of injury by more than half. If the bumps get bad, richen the mixture to ensure no interruption in fuel flow. In moderate to severe turbulence, don't attempt a course reversal.
Turns increase aircraft loading.
Maintain the aircraft's attitude, not altitude. When possible, fly over larger bodies of water. Lakes and oceans absorb heat and thus create little turbulence. If practical, fly the upwind side of a ridge line. As a bonus, you'll pick up a few knots and decrease your fuel burn.