A tip I got on this board was to tip U.S. two-dollar bills for the bartenders and others who get cash tips. You can get them at the bank and when you sit down at the bar for a drink tip the two-dollar bill. Make a big deal out of it and assure the bartender that it is real. The bartender will remember you and give extra good service as a two-dollar bill is something curious and unusual for them. It really worked for us.