You can purchase shipboard credit.......it's like if somebody (TA, family member) gives you shipboard credit. But, if I were you, I'd put that money in a savings account that you won't touch, or even better, 6 month CD.
No you can't pay ahead but like the person said before me Carnival now offers GC's that can be bought before and used on the ship...... also if you are a drinker, and you have an extra $20 laying around and wanting to spend it before the cruise they have drink tickets 4 for $20.
I have a few things we celebrate before our next Cruise in June that I usually get gifts for and I told every this year just order me some Carnival GC's! =
I forgot to add something too, if you don't want to put the money away in an accountant, you can make a piggie bank, I have done this since my 2nd cruise...... I have a big blue piggie bank and I have it sitting on my cocktail table and I just add change to it and $1's all the time and it adds up really quick!
COUNT DOWN ON FOR Glory 06/05
Big Red Boat 06/93
You could go ahead and pre-pay your gratuities. Call your booking agent. That way, there would be a "O" balance when you board the ship - otherwise, the automatics tips are the first thing on your account.
Once my cruise is booked, I start 3 envelopes. 1 for the tips, and 2 for cabs ( each way to and from the port) Every time I go to the grocery store I round my check up to the next 5 or 0 ie... 13 would be 15 or 18 would be 20 etc. and put the money in one of the envelopes. When I get the amount in there I want ($25 for a cab) I seal the envelope and don't touch it. It isn't much, but it helps the bottom line when it comes to cruise time.