I agree with Lucky4Me. Priceline is good for last minute trips, but if you have this much time to plan, they aren't the best way to go.
I checked Bestfares.com twice a day to find out who had the best sales. I'd check in the morning and the evening because it seemed that different airlines updated their prices at different times. Then I would go to the airline web sites or Travelocity (or other) to book. I liked Bestfares because they showed other airports also.
Also, keep an eye on the transportation board. Often, people will post if they see a really great airfare sale going on.
The worst part about starting to look for airfare this far in advance is that most airlines have not released their schedules for June yet.
Try to set an acceptable price for yourself. I was shooting for $100 rt from Dayton to MCO. I ended up booking at $105 from Columbus to MCO and was very happy with that.
Be patient and keep checking. It will save you in the long run!