Interesting article from CNN Money on specific tips for finding the lowest airfares and something really simple like clearing the cookies on your computer so the same search results/fares are not returned when you look up airfares for a specific trip more than once. Also, the tip to search all the major ticket websites, and not just the one where you found the last great deal, as each company makes seperate deals for the prices they offer.

http://money.cnn.com/2006/08/30/pf/airfare_secrets.moneymag/index.htm