Of course, peak is the best chance at good weather and some pool time. But watch for discounts and upgrades offered by many travel agencies and cruise lines. Travel agents can help match travelers and ships and often have access to special discounts. Cruise lines offer air packages and extended stays before or after the trip in the departure city. Or book your own flights, watching for airfare sales.
Lower decks cost less.
Oceanview offers a window. Balcony rooms offer more windows. One nicety that helps cushion the wine bottle prices on Norwegian Sky, for example, is an option to save an unfinished bottle and request it later at any restaurant. WHAT TO TAKE -Binoculars for coastline wildlife viewing. We didn't see any grizzlies, but it's worth searching.