Tipping can be a 'hot' subject here, mainly because of the vast differences of opinion in which are tipped and non-tipped positions. However, as a general rule...
At table service restaurants, 15-20% of the pre-tax cost for good service, 20% or more for excellent. At Disney (and some off-site) TS restaurants, there will be a suggested tip on your check at 18% of the pre-tax cost. For buffets, suggested amount is 10% of the pre-tax bill.
For bartenders, at least $1 per drink (possibly more for a mixed drink, i.e. cocktail).
For luggage/bell services, $1 per bag
House/mousekeeping, again suggested amount is $1 per person per day. We use
DVC accommodation so don't get daily housekeeping and therefore only leave tips on the days we are due a full clean or trash and towel service. Mousekeeping is not technically a tipped position so whether or not you leave a tip is really up to you. We have often found (particularly in off-site hotels and DVC accommodation) that a good tip for housekeeping can help to get you extra coffee/tea sachets, washing powder etc.
There are pther tipped positions, such as concierge services etc. but, unless you are planning to use them, you needn't worry too much about those.
Any tips on tipping? We hadn't factored it in, and now it seems that the $200 gift card that was in our package will go on tips for the 'free' DDP in our package!
It's a common misconception that the free dining is actually free - you pay for it in other ways, such as paying rack rate for the room etc. However, you would always have to factor in the cost of tips whether you were paying for your meals or not so the food itself is still free.