Lay out your clothes to pack on a bed or other large flat surface. This will allow you to see all that you have and eliminate or add as needed. Dressing for an Alaska trip is much like dressing for an entire year away within the space of a week or two. Since Alaska cruises occur in the spring and summer, you can expect warm days and cold nights, storms and calm. You will need to pack for all of them.
Pack the basics like underwear, undershirts and the like as you would for any trip. Then create separate piles of tops, bottoms and outer gear.
Place T-shirts for the warm summer days, which can range into the 70s, into the tops pile. Add polo shirts and light casual dress shirts for formal lunches or informal dinners on board. Add at least one sweatshirt and one fleece for the sudden chills that come on when you are at sea. Light thermal long-sleeve shirts are a great way to stay warm while taking up very little space in your bag and provide a very warm layer with little weight. Don't forget a formal outfit or two for gala dinners.
Collect some shorts for the warmest days, cargo pants for excursions and a pair of jeans for cool and casual times in the bottoms pile. The ideal pants will be zip-aways, which transform into shorts when you need them. Sweatpants are essential gear for the cold nights.
Take a fleece hat with earflaps and a good solid parka. Both are key elements for Alaska excursions into the wilderness or onto glaciers, where altitude and wind can lower summer temperatures dramatically. A waterproof jacket is also a necessity any time you are at sea. For your feet, bring sneakers for downtime on board, hiking boots for on-land treks and dress shoes for dinners. Deck shoes or loafers are fine for lunches and a pair of flip-flops are standard issue for any cruise with pools and spa time involved.
