You can join while on the ship. After the first cruise is completed you will be a gold member. On your next cruise you will receive a coupon book to use on the cruise. Also, you will find some discounted prices some future cruises. After 5 completed cruises you will be a platium member and get a lot more perks. You will have boarding priority and special parties. After 10 completed cruises you will get even more. You will be able to use the concierge lounge from 5pm to 8:30pm. You will be able to have free drinks in the concierge lounge during those hours. A great perk! You will also get a $200 discount off any balcony cabin. After 24 completed cruises you get even more! I don't want to mention bridge tours here because oppis will jump all over me
. But, it is a perk. There is a list of all the membership status on RCCL's web site. It's free and it's the best loyality program of any cruise line.