(Speaking for Port Canaveral) Unless it's your once in a lifetime cruise, don't bother arriving super early unless there are ticketed events you need to get onboard to obtain. Arrive at the terminal after 1:00, usually no line for check in or boarding the ship and your room is ready at 1:30 so you can go straight there, drop off any carry on items and then go have lunch.
Again, unless it's your only cruise where you need to experience everything, ride the AquaDuck on Pirate night after dinner. No line whatsoever. I personally prefer doing this over leaving
Castaway Cay early as that is the other best time. I like all the Castaway time I can get! lol
Don't be afraid to ask for something. If you don't find something you like on your menu that night, ask for alternatives. Most of the servers are more than happy to grab you something from another of the restaurants if they can and have time. At the same time, don't abuse that option and if you do ask for something out of the ordinary, please tip them appropriately. If the servers are willing to step up their game for you, please be willing to do the same for them
(My personal thoughts and opinions of course.)