Rule # 10 of Defensive Driving

10. Always Signal Your Intentions

Be careful not to send the wrong message. For example, if you are approaching an intersection, and you intend to turn right immediately after the intersection into a service station, be careful not to signal too soon. Oncoming traffic may think you intend to turn at the intersection rather than beyond it, and they may turn left in front of you. Finally, always use your signal before you start a turn or a lane change.