I will book when I get a fare that I'm willing to pay. If you are flying from a market that has a "discount" airline, look into flying down on one airline and back on another. I do that frequently with jetBlue and Song out of BOS. Nowadays a lot of airlines are charging one way fares, so these is not the "One Way penalty" that there used to be. jetBlue, Song, Southwest, Air Tran and Independence Air all book one way fares.
I can also use SW out of PVD and then either Song or jetBlue back to BOS as I use a limo service to the airport and this company charges me the same going to either Logan or Green from my house. I have been able to get great fares by being flexable this way.
For example, last week I got SW at $121 RT including all taxes and fees from PVD. Next month, I could not get a good return fare on SW, so I booked SW out of PVD down ($55) to MCO and Song back to BOS ($79).
Sign up for all of the airlines FF clubs that service your airports as they frequently offer email specials.
HTH