I do sometimes feel guilty for going there so much.
If you are planning to travel anywhere my advice is do your homework. I learnt so much from travel books at the library. For flights, watch for seat sales. Try to plan your holiday in the off season, everthing is a little cheaper and there are less people. For us the best time to fly to Hawaii is April. West-Jet has great seat sales then.
Don't feel limited to just Hotels, VRBO and vacation rental website has some great places to stay. But do you're home work about those too. Most people we've interacted with are very nice and curtious, but I've heard some are not.
Tripavdvisor.com has lots of info on everything. Josh found us some amazing little places to eat, with great prices and good food.
Have an idea of the activities you want to do. Try to find the less expensive ones. Tours can cost a lot more then just going there on your own. Most places are pretty self-explanitory, but if you're visiting a Volcano then maybe it might be good to have a guide!
We didn't do everything we wanted to do, and we always spend a bit more then we planned. Mostly on the Kona coffee!
Every place has it's treasures and dangers too, so read up! There are great books at the library and great resources online too!
Above all relax and have a good time!!
This is Hanauma Bay
Josh and I after snorkeling Hanauma
The view of Rainbow Beach while horseback riding.
Walking Tree at Waikiki, with a pretty lady swinging in it
Eating shrimp on the North Shore!