We are a kind and gentle website! You drop your main baggage off with the porters at the pier. They will load these in transfer containers which are then loaded aboard the ship. The ship's staff will then sort through the bags and deliver them to your cabin door. This can take a while and it is not uncommon for your baggage to not show up for a few hours. Don't worry though. It'll get there. The porters like tips too, so be ready to palm them a few bucks when you hand them your baggage on the pier.
It is always a good idea to carry some extra clothes in your carry-on bags. I always toss in a bathing suit and flip flops, a fresh polo shirt and a pair of pants, and a pair of shorts. Naturally you will have any meds you take, and your valuables, in the carry-on.
Cabins may not always be cleaned when you board. This really depends on when you get there. If you arrive at the pier early - say 11am or noon - and they allow you on the ship early, they may tell you that the cabins will not be ready until 1pm or so. If so, you can sometimes run to the cabin and dump off your carry-ons. But they may have someone in the passageways preventing you from doing this. No biggie. Just go grab a bite at the buffet and relax.