It is generally okay to allow the cruise line to select your cabin based on the class you choose to save money. There is a risk of low privacy, high noise and/or high motion cabins.
Cruise cabins are small for even two people
Divide storage locations for each occupant
Decide on if there is an option to have sex in the room:
Decide on who sleeps in the third and/or fourth bed:
Decide on lights out time
Decide on bathroom times in the morning
Keep your clutter to a minimum at all times
Decide on if you want a drink package upgrade (Carnival, Norwegian and Royal Carribean):
Decide on if you want a dining package upgrade (Norwegian and Royal Carribean)