I'm not familiar with flights from TN but I can give you some general info.
1. Always go for non-stop flights if the price difference is no more then $50 on a round trip ticket.
2. Check discount airline sites to see if any operate out of an airport that is convienent for you. [JetBlue, Delta/Song,AirTran,ATA,Southwest,etc]
3. Based on my experiences flying from the Northeast my quess would be that any price below $150.00 round trip would be great and probably should be gobbled up ASAP.
4. Since these discount fairs are non-refundable I recommend that you look into trip insurance just in case you must cancel for some reason.