I absolutely loved the two short cruises I did with mum.
When you board your suitcases will probably be taken away and you'll find them at your cabin - you may well not be able to access the cabin immediately as the previous occupants will be clearing out! So ensure you gave any essentials. Maybe swimming things, or go for lunch.
You'll probs have to pay for WiFi if you need it for work or Instagramming your way round.
Take evening dress for formal nights.
Do everything on offer that's included. I was so impressed with the shows - cruise ship entertainers are pros.
I attended several fascinating talks on history, jewellery and art.
Excursions can be fun - choose carefully. And be absolutely clear on what time to be back on board as they will leave you behind if you're late...
Be hygiene-aware. Washing hands, careful about buffets, loo hygiene etc. Norovirus has been a thing on some ships ...
I found a small swimming pool at the back of one ship with its own little bar, took a book and had a quiet hour while mum was resting.
Explore the whole ship and see what it has to offer.
Remember your chargers. You probably won't need adaptor plugs but double check.
Have fun.