You can either give it to them in cash or go to guest services and charge it to your account, they will give you printed stubs which you would put in the little envelopes they provide for you and give them usually on the last night of your cruise .... Here's what was on the
Disney Cruise site to give you an idea of the tip amounts for each:
What about gratuities?
We'll make it easy. It is customary to give gratuities in recognition of service, which you will most likely be treated to in abundance aboard the ship. As a guideline, may we suggest the following:
Per Guest per cruise 3-Night 4-Night 7-Night
Dining Room Server 11.00 14.75 25.75
Dining Room Asst. Server 8.00 10.75 18.75
Dining Room Head Server 2.75 3.75 6.50
Stateroom Host/Hostess 10.75 14.50 25.25
Dining Manager Your Discretion
Room Service Your Discretion
For your convenience, a 15% gratuity is automatically added to bar, beverage, wine, and deck service tabs. All gratuities can be charged to your room charge.
At the Walt Disney World® Resort, 15% is the customary gratuity at restaurants and bars.