The industry stand is:
Waiter - $3.50 per person, per day
Cabin attandant - $3.50 per person, per day
Asst. Waiter - $2.00 per person, per day
There is also the head waiter, that you may want to tip as needed, totally up to you if he/she does something special or does come around and talk every evening.
Be sure to check your cruise docs and see if these amounts are correct and have a great cruise!