Check with a bicycle dealer for an appropriate lock. If your bicycle is not secured to a solid object, all a thief has to do is pick it up and carry it away. This has happened before, don't let it happen to you. This provides important information to help recover your bicycle if it is stolen, and helps the police get it back to you if it is recovered. Learn to look back over y our shoulder without losing your balance or swerving left.
Some riders use rear-view mirrors.
Always look back before changing lanes or changing positions within your lane, and only move when no other vehicle is in your way. Go slow on sidewalks and bicycle paths. By law you must give pedestrians audible warning when you pass. Don't cross driveways or intersections without slowing to walker's pace and looking very carefully for traffic from behind, especially traffic turning right. Ride in a straight line whenever possible.