Good Advice. Sometimes negotiating down is better then not paying at all. Depends on the scenario. Although if you are aware of how the system works, you can better get away with standing your ground. It's also good to keep a copy of some of the local laws and policies readily available on your phone and maybe links to certain government websites and friends in power. In my case local traffic officers in the Philippines tend to threaten to keep your license if you dont "pay the fine." Having the guidelines for the local traffic agency readily on my phone that states they cant take your license for any reason has gotten me out of so many fraudulent traffic stops. See my main comment to Heidi's post to read more.

Anyways still good advice