If you don't mind, where are you flying from? The standard here is about 600 per but everytime I've been able to get it for 250 - 350. Which airlines to check and when will vary a lot depending where you are.
1. First step for airfare, dont ever bother with a TA, they will not juggle the dates or times and airfares as much as a person could do in 5 minutes from home. The days of them having exclusive access to ticket warehousers seems to be gone too.
2. Fly on Tuesdays and Wednesdays if you can, those cheap tickets go slower.
3. If you're flying less than 6 weeks from now, you probably won't get a decent airfare. 4 - 5 months out seems to be best, before that there aren't many discounts and after 2 months there are very few none.
4. Check daily. I've seen them drop from 500 a person to 250 over night, limited availability though, those seats don't last. Sometimes expedia tells you how many they have access to at a certain price when its a seat sale, and it usually starts at 8 or so.
5. Seat sales can be triggered by company A doing something loopy like expanding service somewhere or slashing fares elsewhere, if you see something like that in the news, look into tickets then. I think I got mine this year when Jetblue or someone went into san francisco, somewhere well south anyways. Could be fluke, but but pretty much all prices dipped considerably.
For me, this time I went with AA to orlando with a stop over in Chicago (there is one airline that flies direct from seattle (Alaska, and they are tough to get seat sales on for that reason), and the stopover is never long, 30 mins this time), and Continental on the way back through houston. Expedia doesn't charge the double booking fee you should pay when doing two diff airlines, so that saves about 50 bucks per person if you split the airlines.
This site tries to predict fares,
http://www.farecast.com/
And I find expedia to have the best fares because they show you all the fees and charge the least fees, usually.