Tipping Floormen

The following questions are prompted by Andy's post below on collections where he states that he gets more lenient treatment because he tips the floorperson. There has been plenty of discussion on tipping dealers. I have not seen any on tipping the floor. Any general guidelines, e.g. amount, frequency, etc.? Any other thoughts, e.g. conflicts of interest inherent in system, etc.?

A little grease never hurt the pump. Would help in unfamiliar rooms where you could ask the floorperson to seat you in a "good" game, and juice them when you ask.