There is enough to do on Oahu to spend your entire time on this island.  Geographically only the third largest of the inhabited Hawaiian Islands, it is nonetheless home to nearly three-quarters of the state's 1.2 million residents — 370,000 of whom are concentrated in urban Honolulu.  I spent the majority of my time in Waikiki.  Waikiki had everything I could ask for and more in a vacation.  The area is very clean.  I enjoyed walking the boardwalk's along with the many other visitor's who came to get some sun.  Although there are many tourists in and around this area, I didn't feel too overly crowded.  The beaches are made for fun.  There is plenty of beach space, and plenty of people taking part in beach activities like surfing, jet skiing, wind sailing, kayaking, volleyball, and much more.  There is an area on the beach that would sport volleyball nets during the day.  Then at night, the nets would come down, and be replaced by hundred's of chair's for people to sit in, and watch a complimentary movie on a gigantic screen.  It was like a drive-in movie theatre on the beach, without the cars.  I frequented a restaurant/beach bar called Duke's, which was right on the beach.  Every night, they had a band playing, and is a popular spot.  You could spend many month's trying to hit every establishment in Waikiki.  If you like to keep active, Waikiki is the place to be.

   Renting a car for the time you are there may be more trouble than it's worth if you are going to stay around the Waikiki area.  There are shuttles that will take you from the airport to Waikiki for between $6-$8, with your luggage.  Parking may be a problem depending on where you are staying.  If you decide to take a trip to the North Shore for a couple days, you can rent a jeep in Waikiki for under $20 a day.  The great thing about Waikiki is they have a great bus system.  You can pretty much get any where on the island using the bus system.  The system works really well in and around Honolulu and Waikiki.  It seems they have buses running every few minutes. 

   Like any other big city, you need to take precautions when traveling, specifically with your bags and purses.  Always keep an eye on your belongings on the beach.  Don't take anything valuable with you, if you don't need it.  I've talked to numerous people who have found their belongings gone after returning to their towel from the water, on the beach.