How to go about asking for an upgrade on a cruise ship?

By the time you board the ship is the most unlikely time to get an upgrade. If you used a travel agent, she may be able to get one for you. But the chances are slim. Anyways, I got an upgrade once and found out about it 2 weeks before the cruise. At the time of boarding, they pretty much have everyone set in a certain cabin. Of course it doesn't hurt to ask, but just don't get you hopes up.

They only definite way of getting a free upgrade is during a booking with special offers. Most cruises always sail full and therefore don't have rooms to upgrade you to. You could always ask and the worst they could say is no. Depending on where you are sailing out of the people at the terminal wouldn't be much help. They usually work for the port, not the cruise line. The earliest I would ask is when you receive your room key. If they can't help they will tell you. Next I would try the guest services desk. I recommend going there as soon as you get on the ship because if they do give upgrades I assume it would be first come first serve. Also half of the guests will be heading to guest services as soon as the board so you will want to beat the crowd.

They don't. Don't bother trying. Everyone would like something better than they paid for.