I've never really understood what "Due Diligence" means, but I think it has something to do with making sure everything is comme-il-faut before you proceed. Whatever it means, the thought of having to do it annoys the hell out of me.
Perhaps if I had done a little diligence, however, I would have known you can't just walk into the George Bellows show at the Metropolitan Museum of Art carrying a George Bellows oil painting wrapped up in a shopping bag secured with duct tape.