I haven't done DCL myself yet but from my research it is one of the last cruise lines to not charge a set gratuity fee to your account. They give you tip envelopes the last day of the cruise so you can give cash - or the receipt.
One point that would be nice to clarify for us newbies, I saw that you actually physically hand the envelopes to your server, room host, etc? What happens if you miss someone, just leave the envelope with guest services? I had assumed there would be somewhere to turn the envelopes in rather than handing them out. I always miss someone (I missed the photog assist at my wedding and wound up mailing it to him!) and would like to not run around the ship on the last day.
DCL does not auto add the tips. THere are several ways to do it:
1. Add them to your account before you cruise.
2. Pay them at guest services via a form after the first night and before the last night.
3. Pay cash in the envelopes provided.
If you prepay before sailing or at guest services, you will receive 2 part tickets, one for each person in the amount you specified, either standard or what ever you decided. One part of the ticket goes in the envelope, you keep the stub. it is customary to hand out the envelopes on the last night at dinner for the wait staff, however you can leave the envelopes on the table, they will get them. You can leave the envelope for the cabin steward on the dresser or bed, and it will be picked up. If you do pre pay, you do not have to hand out the envelopes, they will get the tip on their pay check. But I think it is nice for them to know ahead of time.
I love the pre pay before I sail option, it means one less thing to think about during the cruise. However, I do bring more cash in case I want to show my appreciation for great service.
If you are paying cash and you miss someone, well, you will see your dining room team at breakfast the last morning, so you can tip then. But if you have prepaid, they will see it on their check. I hate to not hand out the envelopes because I don't want to be thought badly of. I assume you could give the envelope to guest services, but I have not had the experience, I hope someone else can tell you for sure.