Here are my suggestions:
* First and foremost: learn and follow the rules of the road for bicycles in your particular locality. Some of the above suggestions may not even be legal depending upon where you are riding.
* Make sure your bike is equipped at least to the minimum requirements - more if you are riding at night or on busy streets.
* Riding on sidewalks seems safe, doesn't it? But is probably more dangerous than riding on the road (particularly at driveways and intersections where cars aren't expecting to encounter bikes). Don't do it unless the law leaves you no choice.
* Don't be afraid, but don't get cocky, either. Motorists can be idiots, but don't get all in somebody's face unnecessarily. Don't end up "right and dead".