DO i need a passport?
Please reference the State Department and this site for more information and pay attention to disclaimers. Also, this may help: https://www.ncl.com/freestyle-cruise/cruise-travel-documents
I want a cabin for one. can i have a cabin for one?
You can have a cabin for one, but you're going to have to pay for a cabin for two. All prices are based on double occupancy in each cabin.
I don't know who i am going to travel with yet. should i wait?
That's fine. Just book the cabin know you will have to pay for two if you don't find that roomie. You can add a name up until a few weeks right before sailing.