I agree with most of the people here about being respectful of cops and they'll basically leave you alone.
Cops get a bad reputation because of some bad apples, but in general, it's just another profession. Most of them just want to get their paycheck with as little work as possible. For a cop to hassle you, that's extra work when you're not hurting anyone. And for a cop to take you in, that's even more work, including paperwork.
I'm new here in case you couldn't tell by my post number or join date (researching my first hitching trip), but I've had enough experience speaking with cops. Even the one time I was arrested (in Manhattan), the cops were pretty cool and didn't even cuff me until right before we entered the station.
Anyways, it's easy to get caught up in the 'F- Tha Police!' hooplah, but most of them are just people, trying to make a living.