When you are in the airport, get the free brochure "101 things to do in oahu". If you have any friends in the Islands ask them to mail you one.:biggrin:
You might want to go to Koolau ranch and do some ATV, and snorkel at the private Island. I have a couple of houses and an office in Oahu. I go there every 2-3 months, and never run out of things to do.
Remember, Honolulu and Waikiki are not what the Island is about. Consider the polynesian cultural center, Waimea gardens. Bishop museum will teach you about all the crap Hawaii has had to put up with, and will give you some insight into some of the feelings of the locals. (trying to be diplomatic).