Okay, so I know I'm back from Hawaii, but everyone wanted me to write a blog on Hawai'i anyways just to give them advice I guess. So, as far as travel guides, I used Fodor's, which I LOVED!!! Hands down, the best organization in a travel guide. Too bad Fodor's doesn't have guides for Europe.
As far as Oahu is concered, if you are staying around Honolulu and Waikiki, you do not need to rent a car. Taking the bus is extremely easy, and shuttles are always available. Also, going to Germaine's Luau, the cost includes a tour bus picking you up at a hotel. But at all other islands, a car is a must. Buy your own snorkel gear, you can get them pretty cheap at the million ABC stores in Hawaii, this will save you money because you can snorkel at every beach, every island. And please wear lots of sunscreen, I promise you that you will burn if you don't.
In Maui, if you do the road to Hana, it's going to be hard to spot all the "stops" listed in the book because the road doesn't have signs for all the stops. Make sure you bring water shoes because the beaches have coral or rocks and you will easily get cut! I should know, I sliced my toe big time. And buying certain things before you arrive are cheaper, like underwater cameras, and plane tickets for island hopping. Also, I know you wouldn't think so, but bring a sweater. It can get cold at the craters or volcanos. Also bring good boots, like Timberlands, to the volcanos, the lava will destroy anything with weak soles.
And for the ladies, if you wear the flower in your hair on your left side, that means you are a taken lady, on your right, you are single and ready to mingle, which isn't such a bad thing since the hawaiian surfer boys are gorgeous and friendly! So, I hope this was a teeny bit helpful , if you have any questions, ask!