Get to know the cops that will inevitably be sent out to monitor you guys. Let them check out your cars. Talk to them. Show them respect. Make them feel welcome, not make them feel like they are "the man".

It's important to establish a good rapport with the authorities. If you can show to them that as a whole, you guys are there with good intentions and that it is only a small minority of people that ruin it, you'll find it becomes easier to establish a spot without hassle.

Also, having a more open-minded police force actively strolling around the various groups will help to deter any stupid behavior.

Remember, the police aren't there to ruin your fun. They're there to do their job.