I tip 20% for good service and 15% for average service in a restaurant (Disney almost always gets 20%). If it's really bad service, I tip or don't based on the mood I'm in.
I tip $1 per small or medium bag and $2 per large bag with bell services. Generally, the two of us travel with 3 22" suitcases between us (a tad too large for carryon), so I'll just tip $5 (I hate carrying ones). I would tip similarly for a shuttle driver who handled my luggage. I'm less likely to tip if the driver didn't handle my luggage and provided no other service than driving. I'll tip a tour bus driver if there's a 'tips welcome' environment. Sometimes they've made clear tipping is not expected.
Valet, I tip $1 - $2 depending on speed of service everything I pick up and drop off the car.
For maids - it's generally considered a non-tipped position, but they are often at the low end of the payscale so many frequent travelers tip, particularly at a Disney venue. $1-2 per night per person, depending on the level of work they have to do. We usually straighten the room our self and put the used towels on the edge of the tub, so we tip $1 per person. Personally, I recommend tipping maids on a daily basis (leave on pillow or with a note stating "thanks", or else they won't take it). Housekeeping shifts vary, so you won't necessarily get the same person each day.
For room service, I'll add on a couple of bucks, depending on whether the tip is automatically added to the bill. I think it is at Disney. If the tip isn't added, I'll tip 20%.
Beware of tip jars in counter service restaurants outside of Disney. There is no expectation of tipping at Subway, Dunkin Donuts, etc., yet they'll put a jar out for you. You order a #1 combo and they want a tip? Geesh!!
However, if the person at Starbucks goes through a lot of trouble to get my complicated coffee order exactly right, then I'll tip.
Have fun with your trip!
Dirk
