If you're one of my friends, you'll want to read this article on nolo.com:
Things to remember when you're stopped by a Police Officer
Totally, bar none, take notes on this one: MAKE THE OFFICER FEEL SAFE!!
I have been let off on several trivial tickets for this behavior. Especially in high risk areas like big cities or dark areas, cops love it. I mean, like I've been thanked before for doing things to help them know it's safe to approach me.
Many thanks to Jack for the link. I've learned alot of this the hard way, and it's good to have it documented somewhere so others don't have to.