Pinpoint the off-peak days to fly within your travel window.

A lot of people focus on meeting advance-purchase requirements, but it's more important to consider day-of-week and time-of-day price fluctuations, says Harrell. "Going on a Monday or Tuesday versus a Friday or Saturday makes a bigger difference in your fare than whether you buy your ticket 6 weeks out or 12 weeks out." If you go to Orbitz.com's Quick Search box and click on "Flexible Dates," you can find out which period of time during your travel window will yield the lowest fare, given the length of your specific trip, and also which 2- to 16-day stretch during any 30-day window will yield the best fares to your destination.

Consider all airports serving your route.

BestFares.com's Quick Fare Finder works for this. Just check the box marked "Compare Alternate Nearby Airports." If you select three departure and three arrival airports, you'll get a list of nine different airport-to-airport options and the lowest round-trip fare for each. Say you need to go from Washington, D.C., to Miami. You might learn that flying from Washington Ronald Reagan Airport to Fort Lauderdale will save you $150 per person over flying from Dulles to Miami. "Don't make any assumptions ahead of time as to which two airports will be the cheapest to fly between," warns BestFares CEO Tom Parsons. "You can't predict it. It depends on the day of the flight."

When comparison shopping among airline sites, make sure your fare searches are valid.

"Orbitz doesn't carry Southwest Airlines inventory," points out Brancatelli, "and Kayak and Sidestep don't carry American Airlines inventory. There's no one best source for the lowest fare." Therefore, be sure to comparison shop among sites. Should you return to an airline's site multiple times on the same day to conduct the same search, clear the cookies from your computer between searches, advises Orbitz's senior director of merchandising, Heather Leisman. Otherwise, some sites recognize you when you return—because they've added a cookie to your computer—and, instead of initiating a new search, will spit out the same results you got earlier in the day. By deleting the cookies, you'll be doing a "live search."

For island resort destinations, think airfare-plus-hotel packages.

"Packages are the great airfare hider," says Harrell—which is why carriers love them: They can discount their fares significantly without advertising the fact. Some resorts in the Caribbean are joining with airlines to offer packages where the airfare is thrown in for free or close to it (see "The Perrin Report," October 2008).

Consider connecting flights.

With the domestic flight cuts, certain carriers have pulled out of markets. Many city pairs now have only one nonstop player, which has shot fares skyward. How to suss out connections that could save you hundreds of dollars? Say you live in Chicago and want to go to Hawaii. Sign up for FareCompare.com fare alerts to Honolulu not only from Chicago but also from hubs west of it: Dallas, Denver, Houston, L.A., Phoenix, Salt Lake City, San Francisco. If you find a deal saving you $500 from one of those hubs to Honolulu, look for a way to get from Chicago to that hub for a lot less.