The Airfare Money-Saving Bible

Ludwig Hamburger, a passenger on British Airways, purchases the first airline ticket sold by the British airline in the new single currency at Frankfurt's Rhine-Main-Airport early January 1. The euro was born on January 1 and Frankfurt, home to the European Central Bank, is planning a weekend of festivities to mark the occasion. ??» (Reuters)

It used to be all so simple, back when airfares changed so infrequently that airlines actually printed them on their schedules. You'd call your favorite travel agent to find the best deal, pack your bags and jet off. And there were only two kinds of fares: coach and first class.

Now, with airfares changing, literally by the second, and an alphabet soup of different offers, finding the "best" deal is a challenge.

This step-by-step guide will get you ready for takeoff.

Sign up for free airfare alerts: Why do all the work hunting down a low airfare yourself when you can have someone else do it for free? Many airfare search and listing sites, such as TripAdvisor.com/flights, Travelocity.com, Hotwire.com, Bing.com/travel and, of course, Airfarewatchdog.com offer e-mail airfare alerts when prices go down. This chart compares many of the leading airfare alert sites. (By the way, only Airfarewatchdog lists fares on Southwest Airlines).

Learn about sales on Twitter: Because some of the best unadvertised airfare sales last only a few hours (even if they're good for travel over a long period), even the best-intentioned email alert can be too late. The beauty of Twitter is that it's instantaneous. Many airlines and alert sites now tweet this deals instead of emailing them.

Get e-mail from your airlines: Next: Sign up for e-mails and frequent flyer programs. Airlines are trying to woo customers to book directly with them by offering special deals when you subscribe. Sign up for emails from foreign-based airlines and from U.S.-based carriers.

Next step: are you a flexible travel date flyer? Doesn't really matter when you go as long as it's cheap? Some websites offer flexible date search up to 330 days ahead; others (mostly those powered by a company called ITA Software) only do searches in 30-day increments. Read more about flexible travel date searching. These sites can be helpful if your dates are set, but you also might want to try "meta search" sites such as Kayak.com, Tripadvisor.com/Flights and Momondo.com. Warning: None of them include Southwest's fares, however, or fares on the smaller but growing Allegiant Airlines.

"Meta search" vs. online travel agency: So what's the difference? For one thing, online travel agencies such as Expedia have toll-free numbers with agents standing by to help you book or re-book a flight; meta-search sites don't. But there are many other differences. Airline websites sometimes have the best fares Increasingly, airlines aren't sharing their very best fares with third-party sites such as Kayak. Case in point: recent fares to London from the West Coast for $420 round-trip including tax that were only available on Spanish airline Iberia's website (similar fares were twice that elsewhere). So once you've found a fare, definitely check airline sites directly.

Watch out for promo codes: From time to time, you'll receive promo codes in your e-mail because you signed up for e-mail from your favorite airlines and online travel agencies. These codes can only be redeemed if you book directly on the airlines' websites, another way they try to cut out the middleman. (Airfarewatchdog lists any promo codes we find on the AirfarewatchBlog).

When to use your miles: Rather than cashing in 25,000 or even 50,000 miles for a domestic economy class ticket that might have cost you $250 or $300, why not splurge for a trip to Europe (50,000 miles on some airlines) that might cost many times more? Or upgrade your $400 economy class seat to a $2,800 business class fare for 30,000 miles on domestic routes? A general rule: if the economy class fare is $400 or more, spending 25,000 miles is a good deal. Less than that, you might be better offering paying cash and saving your miles.

Getting the best last-minute airfares: You'll often get the best fares if you book at least 7 to 21 days ahead of departure. Otherwise, your best bet is Priceline.com's "Name your own price" feature or Hotwire.com. Also take a look at Lastminute.com which packages last minute airfares with hotel and rental car deals -- sometimes for less than what you'd pay for airfare alone.

When to use a real live travel agent: As good as do-it-yourself online sources can be, your friendly neighborhood travel agent may have some tricks up her sleeve to save you money. Let's say, for example, that you get an airfare alert that fares from Houston to Honolulu are $800 round-trip. But who knew that Dallas to Honolulu, same dates, is $300? Or that you can fly from Houston to Dallas for $100 and connect onward? A savvy travel agent.

Getting a refund when the fare drops after you buy: Several domestic U.S. airlines will give you a full refund, in the form of a voucher good for future travel, if the airfare drops between the time you buy and time you fly -- if and only if you fly on the same itinerary. Find details in this chart.

Factor in the fees: A low fare on one airline could turn out to be not so low once fees are added on. Airlines are making most of their profits these days not from selling you airfares but with all those fees for baggage and other perks. In addition to checked bag fees (chart) there are even fees for using your frequent flyer miles and for other services such as changing a travel date or bringing a pet on board.

Is there a "magic" hour or day to buy? In a word, no. It's true that the airlines' weekend deals come out Monday to Wednesday, and some airlines announce their sales early in the week, but if you limit yourself to searching just on those days, you'll miss out. A good fare can pop up any moment of the week.

Best days to travel: Although a low airfare can appear at any time, one thing's for certain: it's cheaper to fly on a Tuesday or Wednesday. Saturday is also a low-fare day. If traveling internationally, Monday to Wednesday is often the sweet spot.

Airfare predictions: Speaking of "when to buy," Bing.com/travel purports to offer accurate airfare predictions, indicating whether the site thinks a fare will go up or down, and it's certainly worth a try, but it's not always accurate. To see if an airfare is currently on the high or low side, do a web search for "historic airfares" to see airfare trends on a particular route. Two useful sites: Farereport.com and Kayak.com/trends.

George Hobica is a syndicated travel journalist and founder of the low-airfarelisting site Airfarewatchdog.com. Follow Airfarewatchdog on Twitter @airfarewatchdog for late-breaking unadvertised airfare sales and air travel advice.