A lot of it depends where you're flying from and what airfare looks like year over year, $300-800 could be cheap depending on where you're going from, how many stops there are, and how many flights go out of your airport.

Airplanes tend to be filled completely now so when the number of seats start to drop it won't get cheaper...

I booked 1 1/2 months out and got almost the lowest price possible, the previous time I booked 6 months out and overpaid.

Google.com/flights shows a LOT of different sites and is an aggregator of airfare, it's easy to use and lets you quickly search for airfare.

Mon/Tues/Wed are "usually" the best time of the week to search.

One thing to keep in mind that if it spikes from $400-800 then odds are it won't go much below $400, if each person is booking his/her own ticket then you can also use places like hotwire and priceline which often have rebates in the entertainment book.

$20 off x8 is $160 saved.