[TheThinkTank] Bike parking contracts

Howdy all of you out there in bicycle land~

We find ourselves in the wonderful position of high demand for our bicycle valet parking services (no complaints), but we have been burned a coupla times by some of the folks who have engaged us. Because of this, we have decided to draw up a contract that will (hopefully) prevent this unfortunate situation from happening again, or give us some recourse if it does. For those of you who do bike parking, would you let us know of your experience with it, such as what has worked, what hasn't, what you might do differently, etc.? If you have a contract, could you send a copy to me to give me an ideas as to how ours should be drawn up? Much obliged!