Lots of good stuff in this thread, other than the arguments. Other than the obvious "rule following" type advice, I would also say that there are three big general principles to help increase the safety of a newbie to city streets:

1) Don't ride really fast. Lots will disagree with that, but when you're just getting your bearings, going slowly gives you plenty of time to see your environment, and stop if you encounter an obstacle (i.e., doors opening, cars cutting you off, etc.)

2) Be predictable. This can mean a lot of different things, but don't go out of your way to confuse drivers. Ride in a straight line, obey traffic signals (I think this is generally a good idea, until they allow for cyclists to legally treat them as yield signs), go the right way down a street, etc.

3) Be polite. Don't escalate situations more than necessary - you're vulnerable, and some drivers get crazy road rage. That might not always feel satisfying, but I think it's generally a safe approach. I try to remember that at the end of the day, I want to get home to my family in one piece, so no need to be too risky about it.

Ok, fine - #4 Lights! Lots of them!