I have recently started commuting (in the Puget Sound area) and after reading the Advice sticky I have a few questions (or just one very open one). What are some of the no-no's and should-do's when it comes to bike commuting?

When I ask this, I assume the obvious is already out there. Examples: helmet, lights at night, and so on. I am more referring too, when do you use the sidewalk and when don't you? Do you split cars at a stop light and go to the front, or do you hang in the back where you happen to fall? I know this will show a difference of opinion on some things but I am just trying to learn to be a responsible and efficient commuter. Thanks guys (btw, first post, but I have been using the forum for a little while).