You check in and know the ship is only 90% of capacity. Can you politely ask for an upgrade?
Done in the hotel industry all the time with polite chat and may be a little incentive (nudge, nudge, wink, wink). Is it done on cruise ships?
Can you call the cruise line right up to departure and respectfully ask about room assignments or changes.
Look all I want is to be assured I do not have the worst room on the ship on my first cruise and spouse is not impressed (but that's life).