Be flexible about when you want to travel. By moving your departure day and time, you can save big. Midweek travel, travel at night and Saturday flights are usually the cheapest. You can also save when you book 21 days in advance. Just be careful because some discount tickets are "non-refundable, non-changeable." 

If you buy your ticket and then see a lower advertised fare, get on the horn to the airline and demand they refund the difference on your credit card.

Most airline web sites now advertise last minute E-fare travel bargains on undersold flights. Sometimes you can get a great deal on a popular destination. You should subscribe to the email newsletter of any airline you use frequently.

Can't get a cheap fare to the city you want? Do a two-step. Get a cheap fare to the nearest big city and then take a discount commuter the rest of the way. You could save hundreds of dollars.

Overbooking can help you. Sometimes when flights are overbooked, if you volunteer to be bumped you can get rewards such as a reduced rate, a voucher for a free ticket and if you have to stay overnight the airline will probably give you free lodging and food. They will sometimes even bump you up to first class or give you cash.

Consider becoming an air courier. All you have to do is babysit a package that is flying (usually overseas). There are several downsides: you generally can't choose the exact time date and city/airport you're traveling to (Gatwick vs. Heathrow, etc.) and you'll have to do a little administrative work when you arrive. But you will save a lot of money, especially if you can arrange to act as a courier on the return trip. Usually couriers are restricted to carry on luggage.

Hitchhikers Guide to Airtravel:
There are some services available to the very flexible but discount-hungry traveler. Air Tech and Air-Hitch are services that fill empty seats for airlines. They are cheaper than ticket consolidators for one simple reason, you fly where and when they tell you. If you just want to "go away to some place sunny," you give them a five day range of dates you want to depart and a specific city or location. They claim that they will get you there 70-80 percent of the time. The other 20-30 percent of the time they will get you some place close (Hartford instead of Boston, for example). Their ratios on the return trips are about the same. Less than $159 to Europe is a standard fare. Check out their web sites http://www.airtech.com/ and http://www.airhitch.org/.

Procrastiator's Price:
Because plane tickets, hotel rooms and even cabins on cruise ships go bad if they go empty, sometimes you can work some last-minute magic. If a charter, cruise or even a regularly scheduled flight is going to leave in 20 minutes and they have room to spare, walk up to the ticketing agent and ask for a 50 percent discount. Sometimes clerks are instructed to take any reasonable fare to make sure nothing leaves with an empty seat. This is a game of chicken that you can frequently win. Just don't insult the clerk with your offer, be polite and be sure you have everything ready to go.