Check this out...
http://www.youtube.com/watch?v=yqMjMPlXzdA&feature=user
Its pretty long but very informative. It covers the three most important lines you have to keep in mind when getting hassled by police
"Officer, I do not consent to any searches"
"Officer, am I free to go or are you detaining me?"
"I have nothing to say until I speak with my lawyer"
Heres a couple of minute long clips if you don't want to watch the whole thing
How to refuse a search of your vehicle -
http://www.youtube.com/watch?v=nyokKFIecIo and
http://www.youtube.com/watch?v=uV0g5B1blqk
How to refuse search of your home -
http://www.youtube.com/watch?v=PCVnMDy_7nM
How to refuse a search on the street -
http://www.youtube.com/watch?v=KJWFAWqzSds
Getting tricked or intimidated by police -
http://www.youtube.com/watch?v=eOE9feaWl1U