There are lots of newbie bike commuters out there; maybe you're one of them. If so, please read this list and please amend your ways if you are violating any of these laws or guidelines.
Riding against traffic
Running stoplights and signs in the presence of other vehicles (you're relying on them stopping for you to continue living)
Riding at dawn / dusk / dark with no front light and no rear reflector
Sudden left turn from right side of road
Continuing straight through the intersection from the right side of a right-turn-only lane
Riding in the median of a roadway, between the two opposing directions of traffic
Curb-hugging. No, ride in the right tire track, or in the center if there is no shoulder or bike lane
Sidewalk riding where the sidewalk is frequently cross-cut by driveways, side-streets, or it has many pedestrians
No looking back before you make a move
No eyeglasses / sunglasses, sunscreen, water
No personal ID on you
Use a rear-view mirror
Wear a reflective vest and areflective ankle bands in low-light conditions. Wear bright clothing at all times.
Use a red rear light and a red rear reflective in low-light conditions
Carry a cell phone