How to book – Search and book via a travel agent like Expedia.com or cruisecompete.com. If you have to ask something then these travel agents usually provide way better customer service than the ones employed by the cruise company.
Deck – The cruise floors are called decks. Larger the number, higher the deck. Most outdoor activities (including pool, spa, nightclubs) are usually located happen on the higher decks. The lower decks are usually about indoor activities and restaurants.
Bidding – If your cruise line permits, always bid for a better room within your budget.
Formal Dress – Carry at least one formal dress, it can turn out to be useful for some formal events on the cruise.
Diet – Popular dietary restrictions like vegetarian or vegan are not hard for them to meet most of the time. But if you have a more special requirement (like halal diet or kosher), let the cruise ship know in advance.
Meals – Usually all cruise ships have a buffet restaurant and multiple dine-in restaurants. Former is quick and contains prepared food. Latter is fancier but takes its own sweet time. The buffet restaurant is usually on the higher deck and is included as a part of the cruise. Some Dine-in restaurants (high brow term: “Speciality restaurants”) are complementary, some are not. An advance reservation is good to have (but not required) for the latter.
Beverages – While the standard food is free on the ship. Standard addictions like Soda (soft-drinks), carbonated water, and alcohol (hard-drinks) are not free. If you really need them, buy them in advance, buy them onboard (expensive), buy and consume them whenever ship stops at a new destination or look for a promotional package which includes them for free.
Water – Carry a few empty water bottles to refill or even better a hydration pack. A hydration pack is really useful for the day trips at the intermediate stops (fancily called, “port of call”).
Shore Excursions – Shore Excursions at the port of call can be booked via cruise ship or on your own. The cruise ship ones are expensive but are a safer bet. If you are adventurous then book them on your own. If you are not, just go with the cruise bookings.
Guest service – If you need something from the guest service, catch them early in the morning or late at night. Every other time, I have seen a queue. I wonder if they give out some raffle tickets but I digress.