Last summer, my father and I went to a nice restaurant with some of our buddies. For once we had finally be together enough to call ahead and make reservations. When we got there though, they were swamped (partly why we made reservations) and didn't have a table ready for half an hour after when we had made our reservation for.
My dad jokingly asked for free drinks since we had to wait half an hour to get seated, and would you believe it, we got them. It probably helped that we still had a $150 tab, but remember: it never hurts to ask.