005: Get it in writing. No. Really.
I'm including this for my own benefit as much as yours. If you're shooting on location, and it's a location you don't own, get the appropriate paperwork signed up front. Here's an example of a location release, though you should consult with a lawyer (not a filmmaker with a blog) when it comes to this sort of stuff.
As many times as I've been told "get it in writing," and as many times as I've passed that advice on to other filmmakers, I find myself not getting it in writing all the time. And, almost every time, it ends up biting me on the ass one way or another. Even if the person in charge of the location says "no problem." Even if the person in charge of the location is your best friend. Settle on all the details of the shoot (especially the date, duration, and price) up front, on paper, and save yourself a lot of heartache.