Notice that if you ride against traffic, predictability is completely lost! If a motorist sees a car coming directly at him, what will he think? Panic! It's just as uneasy of a feeling when a motorist sees a bicycle approaching — well, an attentive motorist anyway.
Signal your intentions! My preference is to signal with my right arm straight out for a right turn, my left arm straight out for a left turn, my left arm pointing down if I'm stopping or maintaining my lane position when a right-turn-only lane is coming up. Again, this helps with your predictability, which helps you integrate into the flow of traffic.
In California, it is legal to "filter" to the front of a lane of cars, just as it is on a motorcycle. Drivers, however, really hate this. My recommendation, at least in light traffic, is to maintain your lane position at stop lights behind the other vehicles. Bicycles can accelerate faster than cars up to about 15 or 20 mph — for a reasonably fit person. This provides ample time to clear an intersection at a traffic signal. In heavier traffic, because I don't want to stand behind a CO-spewing tail pipe for too long, I'll filter to the front and take my chances. Just be aware that when you filter, you're not being particularly predictable, so be on your guard.
These are some of the most basic tenets to follow in traffic. Be predictable and visible and obey the rules of the road and your risks in traffic will be lower than if you were driving.
(By the way, since biking regularly my blood pressure has dropped from an all-time high reading of 174/114 to regularly about 115/75. It makes my wife happy that she'll have a more relaxed version of me around for a long time.)