Check out the site for the airline that makes the most trips to your destination from your home airport. Enter the trip parameters and check out the prices. Then change the departure and return dates in different combinations to find the best prices.
Some of the travel sites, Expedia, Travelocity, etc. have a box you can check for flexible dates and will do the check for you.
"If you want to make an apple pie from scratch, you must first create the universe." -Carl Sagan