Royal Caribbean is a notch above the likes of Carnival, MSC and Costa Cruises; so expect to pay a bit more. To obtain Royal Caribbean cruise specials:
The only perk which Royal Caribbean sometimes offers is onboard credit. Royal Caribbean aren't known to offer free drinks packages, the best we've seen is them discount it.
Royal Caribbean's loyalty club is called the "Crown & Anchor Society". The different levels are (from lowest to highest) gold, platinum, emerald, diamond, diamond plus and the pinnacle club.
If you achieve Diamond status, you can enjoy an open bar every evening from 16h30 until 20h00; with some restrictions and conditions.