simple savings: airfare

1. Get to know the aggregators. A whole crop of new web sites has sprung up in recent years to help you find airfares. These aggregators search all the airlines' websites as well as search engines like Orbitz, Travelocity and Cheaptickets. This is good because many budget airlines don't sell tickets through search engines. The aggregators also have terrific tools for searching different times of day, different dates or airports (more below). My favorite aggregators right now are Kayak and Mobissimo.
2. Be flexible about when you travel. Unless you must depart or arrive on a certain date, it helps to be flexible on your flight dates or the time of day you travel. The aggregators above all help you search within ranges of dates and times so you can see how much of a difference it makes to fly on, say, a Wednesday morning.  
3. Be flexible about where you travel. If you're flying to or from a major metropolitan area, search for flights in neighboring airports too, a feature most of the aggregators offer. (For example, check for flights to San Jose and Oakland as well as San Francisco if you're flying to the Bay Area.) 
4. Book your flight at least three weeks in advance. 'Nuff said.
5. Check the round-trip price even if you're flying one-way. For some reason round-trip fares are sometimes still cheaper than one-way fares. I have no idea why this is.
6. Get notified about airfare drops, or refunded the difference. Yapta tracks prices and will email you if fares for your particular route go down. And Orbitz will refund you the difference if a ticket you purchased from them later decreases in price. 

Have a great trip!