Do yourself a favor... put out everything you plan to pack on your bed and then put at least half of it back. You will need casual clothes for most days and evenings. There are two formal nights during the week for those who want to get dressed up and go to formal dining. This is optional as there are many other venues to visit that don’t require dress up. Here is a check list of things to bring:
Sturdy shoes (If walking is required on any excursions)
Sweater or jacket (depending on destination)
Magazines or books
This is a partial list; if you forget something you need, it most likely can be purchased on the ship or in port. Just pack as you would for a regular vacation but pack lightly as cabin space is limited and you won’t wear much of what you bring.
With the multiple technologies today remember to bring your various chargers and also you may need electrical adapters for foreign countries.