Be ready for "Traffic Shock", even on Maui and Kauai. On Maui, from Lahaina Town back towards the airport area and on your way towards Haleakala and the Road to Hana, I was surprised to see how much traffic had increased, in the 12-15 years in between visits. Same with Kauai. Just be aware. Can't imagine what Oahu is now like.

Get your reservations for rental car as early as you can, when going between November and February; this is high season. And for some activities like luaus and whale-watching trips, you may also want to look at booking before you actually leave. We waited till we were there on our last Maui trip, and could not book the luau we wanted. Same with sunrise on Haleakala-they are still limiting # of people on top for sunrises and requiring visitors to make a reservation for this. I think none is required for sunsets, though.

Do yourself a favor and check out the "blue book" well before you go; it really IS a great help for planning what you want to get into, including the lowdown on the good snorkeling spots and vendors/trips.

Enjoy!!