15-20% depending upon service in restaurants and bars.

I leave $5/night in hotels for housekeeping.

$5-10 for bell boys(girls) depending on how much luggage they haul. $20 if I think I'm going to need some future special favour during my stay.

$10-20 for hotel check-in people again if I think I may need future favours (more if I discern the chance for, or am given, a room upgrade)

$2-3 for car valets each time I take my car out.

Airport/rental shuttle people get $2-3 if they help with my bags.

$10 for good tour guides whether walking or on a bus.