Southwest was having some seriously crazy fares. 1 ways for $99.00 each way if you traveled on a Tuesday or Wednesday and $159.00 each way if you were traveling on the other days. I am not sure if that offer is still going on. It is worth a try though.
that's kind of a vague question, since we have no idea where you're based or where you're going. we could be more helpful if we knew more.
if you're in the US, sign up for american airlines' netsavers emails.
kayak.com also is great, as is farecast.com.
I just got two tickets to LA for 464 total include taxes and fees. I bid through priceline. The only setback was that we dont get to pick the time. we leave monday so it could be between 6am-12am and come back sudnday and our flight could be anytime between 6am-12am through continental. They'll tell you closer to the time. I cant help you if its international flights.