I've found at some Hilton's when you use a debit card, they charge you the entire amount when they swipe it and don't get an approval hold. At the places that do get a hold, I've seen it in the area others have reported, 20 to 25% of the expected bill.

I worked with one guy who never had any room on his card for the holds, so he would settle his bill every day and have them do the next night, night by night, so he only had one nights hold at a time.