Yes, flying to Hawaii can be quite expensive. But here are some tips for getting the best fares:
1) Consider flying in low season, which is basically from Oct 1 through mid December. Airfares should be generally cheapest then.
2) Usually the cheapest days to fly are Tuesdays, Wednesdays and Thursdays.
3) If you are fairly close to more than one airport, then check each when shopping.
4) Major airlines have deal emails you can sign up for. Go to the website of all the airlines that fly from your airport(s) and sign up.
5) Monitor AirFareWatchdog's website for deals to Kahului, Maui, Hawaii from your local airports. You may sign up with them for email alerts for new flight deals as they are announced.
6) Sign up for Kayak price alerts here.
7) Get an Alaska Airlines Visa card here. It has a $99 companion fare that can be used once per year and it can be used to fly to Hawaii. This is one of the best deals going.
8) Try each of the major airfare websites: Expedia, Travelocity and Orbitz.