I typically get $40 in singles and 5's and keep them in an envelope. When you arrive at your resort, tip the guy who unloads your vehicle. I would do at least 5, or go with the $1 a bag rule. Later, when your luggage is brought to your room, tip the bellman--I think most people go with the $1 a bag rule here--but DH has been known to do a flat $5--a bit skimpy by some standards.
When you phone star services and ask for something to be delivered to your room--robe, extra pillow, etc., $2-3 should be adequate. If you take advantage of the package delivery from the parks, again, $2-3.
If you arrive from the airport via a cab or car service, 20% is customary.