Getting upgrade or even a free cabin? (really).. Write an internet cruise review on your last cruise. Try to relate your ship's observation (while having fun) the operational day-to-day activities of the staff. Highlight the positives while constructively pointing a "there's room to improve" negative. Appropriately comment and commend the hotel director & staff while stating his/her name on the cruise review. Make it a refreshing "make-my-day" review for the corporate folks to absorb. Send it to XXX Cruise Lines, Office of the President... with a "Thank You" greeting card. Almost always, you will get a reply letter with 10-25% off your next discounted cruise fare.
After booking your next cruise, email an "advanced thank you" to the hotel director with the attached internet review of your previous cruise. Do mention your desire for upgrades. If it's a LOW peak season, you will get "token of appreciation" upgrades/gifts galore. When you board, drop an amiable note to the Hotel Dir. Aaah, fine champagne or wine awaits you at the dining table... courtesy of the HD. Did you book 4 of you in a cabin? The HD may just compliment you with an extra cabin, after checking in. RCCL/CCL do appreciate such gestures.
The moral of the story is... the golden rule still applies universally.. & warmly appreciated.