I took my wife out last night for a nice birthday dinner (Del Friscos, Ft. Worth if anyone is interested) When we finished dinner I went and gave my card to the valet to retrieve my car. He came back about 10 minutes later and said it won't start and, "is there a trick to it?"
I eventually hiked over to the lot and got in to find that the battery was completely dead and the headlight switch was on!

I guess most cars they park have automatic headlights....jeesh. Luckily the valet's car was nearby (a diesel Jetta) and was able to jump my car with some very good jumper cables.
Moral of the story......make sure your valet has driven a car that is 10 years or older at one point in his life AND always carry a GOOD set of cables. It helps to have a dead battery around another diesel too