Use a discount card. Several of these are starting to pop up. These are cards that you buy at a fixed price and then you can do as many activities as they support and as you can fit in a day. If you are a very active traveler these will save you a lot of money. Best on Oahu and Maui.Do buy yourself a good guidebook. This book can be very helpful, especially when exploring the towns and other places. Remember that most of the time you will be touring on your own in a rental car so having a guidebook is quite convenient.But before you start packing, consider first how many persons will go on this trip. This is important because some resorts offers great discounts for large groups or family. I also suggest renting a vacation home which is much cheaper and can obviously accommodate more people.