Not exactly the $20 trick, but we always go to Vegas in December just after the National Rodeo and before Christmas.
We always bring a really nice box of Holiday chocolates from a local confectioner in our area. We almost always get an upgrade of some type.
When we went to Golden Nugget this passed December they upgrade us from the South tower to the North Tower. It was really nice and very convenient as the elevators are right off the casino.
So, yes a $20 might work.