Royal Caribbean suggests:
$3.50 per day, per person for Cabin attandant
$3.50 per day, per person for dining room waiter
$2.00 per day, per person for asst. waiter
They also suggest somthing for the Matre'D, but thats up to you, if he does something for you other than just a greeting when you walk in, we usually tip $10 to $20 depending.
It should average out to around $10 per day, per person.