Contact the Norwegian Cruise Line spa through the cruise line, either by phone or by email. Some spas will let you pre-book your appointments online. Spa treatments can include everything from having your hair cut and colored, to a relaxing massage or a mani/pedi for the pool. Spa appointments tend to book fast because they are an indulgence, which is what a cruise is for.
Make reservations for restaurants when you are aboard the cruise ship. Most cruise ships have a few restaurants where patrons can go without making reservations. However, there will be some fine dining restaurants to choose from that will require reservations. Check with the concierge at these restaurants and book as soon as you can.
Consult the cruise ship tour guide for information about day trip excursions. The most popular excursions will book quickly, so it's important to act on this right away.
Make appointments for other miscellaneous services, such as babysitting if you have children traveling with you and you want to have alone time.
Pre-book excursions on the islands or locations that you are visiting prior to boarding the ship. It helps to have a planned itinerary of things to do and see. This will help you estimate what you will need reservations and appointments for.