Hawaii is a beach paradise, and as such you will want to pack shorts, skirts, tank tops, short-sleeve shirts and, of course, bathing suits. No matter what your length of stay, bring more than one swimsuit. You will want to have one dry one available at a moment's notice, and in tropical weather they do not always dry quickly.
While we all dream of walking barefoot on the sand, you will need shoes at some point. Flip-flops are essential for the beach and other activities, but you will also want at least one nice pair of shoes to go out with. Even if you are just going out to dinner, the islands do still have some dress standards for nicer establishments.
With this in mind you will also want to bring at least one nicer outfit to go out with. However, if you are going to a luau, you need not dress up as it is a casual beach event. You may get coerced to go on stage, though, so dress appropriately. The rest of your clothing should be nice but casual resort wear.
One last-but-not-least item is a good bathing suit cover-up---even beach restaurants will refuse you service in a bathing suit, wet or dry. A sun hat is also a good idea, but UV protective sunglasses are a must. The sun in Hawaii is the same sun that you see in your local sky, but there is a reason you burn faster there. You are much closer to the equator than anywhere on the mainland. Even if you are trying to get a golden tan, do it slowly and protect your eyes.
Finally, good sunscreen is worth its weight in gold. Yes, you can buy all of the major brands locally, but truth be told they may or may not give you the protection you need. According to dermatologists, your sunscreen should contain zinc or titanium oxide as the major ingredient in order to gain any protection. If possible, contact your local dermatologist for recommended brands before departing.
