Boarding my NCL cruise to Hawaii 2 years ago, I handed $20 to everyone I saw, saying, "I know you'll take good care of us." Was I ever glad!
Later in the cruise, my new friends couldn't get reservations at the very popular French restaurant, but I always could. And we were able to change to a much nicer table when our friends were told the dining room was too full at the second seating for any moves.
Of course, I also tipped normally at the end.