NCL is freestyle cruising, you can go to MDR in shorts and t-shirt, but don't go in a bathing suit, be presentable. Only a couple of restaurant require gentleman to wear slacks (Le Bistro, Palomar).
The drink package is one of the best out there, but you don't have to drink the whole bar on the first day, it will be open the next day.
Don't be a lounger/pool chair hog by putting your belongings on chair at 8am and returning at 3pm.
You pay a daily gratuity fee per person per day, but if you get good service, it doesn't hurt to tip a little extra.
If you own 100 shares of NCLH stocks, you get a shareholders benefit on every NCL cruise.(Free money)
And as mention above, 10% off for Military/Veteran program.