As said before they can't take money... But they can take "gifts" (take it as you may)
Always a birthday present for my #1 SA. Around the holiday season my #1 SA, #2 SA, and the Service Manager get bottles of hard liquor. I take the loner car girls various things thru the year.
Sometimes I'll just stop by with a Peet's Coffee Carrier just to say hi.
Various "perks" but its more than just that. My family has been going to the same Dealer for at least the past 13 years. They have watched me grow up and have become friends.
Its more than a tip, even after being away for a year, I still got the same treatment as before. Besides who doesn't want another friend to talk about cars with?
Oh and the 10's and mentioning something about the SA on the Survey really help.