I agree with Colin although I think his prices are too high for two reasons.

First, because he lives in an expensive city.

Second, based on an interview I heard on the radio with a guy who wrote a book about tipping. I actually bought the book. He says $20 and the right approach is all it usually takes. Right approach means being discrete and respectful for the hard work someone like a maitre d does. And doing things like being loyal to an establishment, explaining why its important (anniversary, etc.), having the right attitude (consider it a favor, not an entitlement).

He recommends for most things calling ahead and explaining that you'll "take care of him." And then when you show up, fold the bill into your hand and shake his hand with both of yours.

The books main points were
that there is a lot available if you ask for it,
most establishments want to take care of people who are willing to take care of their employees,
and it doesn't take nearly as much extra as you think to get more than the next guy.

That said, getting an upgrade like this was beyond the scope of the book. But the key is that you maximize your chances by asking in a well thought out, discrete, and respectful way.