Haven't found any jerks, either, but I have found quite a few who expect buyers to magically appear with no effort on their part. With art (and you'd think some of these folks would know this) a good deal of communication is needed between buyer and seller. Art buyers are buying a story to go along with the work itself, so sit down with the operator of the venue, over coffee or a beer, and tell your story. If the operator doesn't seem terribly interested, you probably won't sell a lot there. If you can generate enthusiasm, you've found a friend and both of you will benefit.
As for written stuff, I've always used a simple letter of understanding, saying the retailer will carry insurance, will be liable for any damage to the works, will keep the works clean, that I can reclaim the works at any time after a certain period, that the works belong to me (that's very important if the venue goes bankrupt, otherwise the work goes into their asset pot), specifying the revenue split (I have one place that works 30-70, with me on the long end; that's unusual though), and that they will pay within 30 days of a sale. My lawyer tells me that such a letter becomes a contract if there is no other written communication from the venue, but it's better to have a signature and date from the operator on it.
A good place to find information on art law is
Carolyn Wright's site.