Cheap Airfare Tips

Book Early
Airline ticket prices typically go up 21 days, 14 days, 7 days and 3 days before departure, so if you're looking to save, book before these deadlines.
Book Late
You didn't like the last bit of advice? Ok! Sometimes you can buy tickets at the very last minute for a great price, if the airlines have failed to fill their planes. Many airlines offer weekly newsletters that feature their best last-minute deals. Remember, however, that during peak travel periods, making reservations late in the game can cost you a lot of money.
Shop Around
No matter how good it sounds, you should never book the first fare you see. Start your search by checking a few of the major online travel providers, like Travelocity, aggregator sites like Kayak.com or consolidators like CheapTickets.com. This will give you a preliminary idea of which airline flies your particular itinerary, what the going rate is and what restrictions might apply. Armed with this information, you can head directly to the appropriate airline web site to see if the same flights are any cheaper (some airlines guarantee to offer the lowest possible fares on their own Web sites). While you're there, check to see if the airline is running any sales or promotions to your destination.

If you don't see anything in your preferred price range, don't be afraid to bide your time and watch the fares for a bit. Most major booking sites have alert features that will e-mail you when your fare drops to a price you're willing to pay.
Know When to Buy
The hardest part of booking a flight is knowing when to stop tracking fares and make that final purchase. Bing Travel can help you reach that decision, offering fare predictions for most major cities. Just plug in your itinerary and the site will advise you either to book now or to wait, depending on whether the fare is expected to rise or drop. Another useful site is Kayak.com, which displays the fare history for domestic and international flights, allowing you to see whether your fare is headed in an upward or downward direction.
What Day to Buy
Most airlines launch fare sales on Tuesdays and Wednesdays -- so if you decide to buy on a Monday, you may be wishing you had waited when your destination goes on sale.
Be Flexible
If you live close to more than one airport, check out the fares from all of the airports near you. Many online fare searching engines will ask you if you are willing to depart from or arrive in more than one city. "Yes" is a good answer! Also, experiment with different travel dates; shifting your itinerary by a week or even a few days can make a significant difference in fares. You'll usually find the best deals on Tuesdays, Wednesdays and Saturdays.
Don't Forget the Discounters
Discount airlines can save you a bundle, but shopping for fares can take a little longer, as some still won't play with the aggregators and booking sites (Kayak now offers fares for JetBlue, Spirit and AirTran, for example).
Group Fares
Traveling with a small army (or least a couple of adults and all the kids)? Check to see if the airline has group fares. It will take browsing to another page on the web, or using another phone number, but many airlines will offer discounts for groups as small as eight. If your troupe doesn't make the size cut, consider traveling with another family so both can take advantage of the discount (usually in the 5%-10% range).
Use Your Frequent Flier Miles
Why pay a fare at all when you can use your frequent flier miles? Although redeeming miles has gotten more difficult in recent years, it's still a good option to consider, particularly if you're booking early; airlines designate a very limited number of seats on each flight as eligible for award travel, and these seats go quickly.
What Goes Up ...
If fares go down after you've purchased your ticket, ask for a refund! You may not always get one, but policies vary by airline -- and many do not publicize the fact that they will refund you the difference if prices go down. It can't hurt to ask.

Yapta.com is a site that will track flights for you after you purchase and notify you if the fares go down.