One of my favorite ways to find cheap plane tickets is to set a 24/7 alert at an airfare deal monitoring site. These services are amazing and every so often you can even jump on a 'mistake' airfare. You have no doubt heard the stories where the airline accidentally sold a ticket for $20 that was supposed to be $200; the people that get these deals are usually set up with 24/7 airfare monitoring. It is free to set up these alerts, and there are a number of different sites with a wide array of features to choose from. The best way to take advantage of airfare alerts is to be as flexible as possible on your travel dates and jump on a deal when it becomes available.
Here is a great list -
Airfare Watchdog (my favorite)
Helping you make the most of God's money!