I'm almost positive that this is goes for any of the Carnival ships:
When you automatically get something like a drink, a 15% tip is automatically added (I got a drink for $3.50 and the receipt said $4.03). You have to have a sail and sign card to get anythign on the ship, so the tips are automatically added.
On drinks they do add the tip to your card. As far as your steward, waiter, etc. There are some great guidelines as to how much you tip at the end of the cruise out on the web. On Carnival you will tip at the end of the trip in cash for all the above. Carnival will put a sheet in your room giving guidelines. Tip according to the service if you do not agree with them.