Stay over a Saturday night

This is the golden rule of flying round-trip. Remember that business travelers tend to want to be home for the weekend. Occasionally, a low fare will be introduced that does not require a minimum stay.

Buy more than 21 days in advance

If you are making inquiries into flights that are sooner than 21 days from now, they are likely to be more expensive. Not only do airlines like to be able to plan ahead, but they also figure that if you have to fly on short notice, you may not have a choice. The advance purchase schedule varies from 21 days to 3 days. Occasionally there will be special 3 day advance fares. These generally appear during fare wars and last only a short while.

Use the same carrier for all flight segments

When making more than simple one way or round trip reservations, using the same airline for all the flights of your trip will often result in significant savings. Simply picking the cheapest individual segments regardless of carrier will not result in your best travel value. In some cases you may have to change your airline preferences a few times in order to get a return with a consistent carrier for all flight segments. Choosing "none" as a carrier preference is sometimes a good way to get a general feeling for which airlines service the most number of airports in your trip. Many times on international inquiries, two or more carriers may be mixed on the same choice when a connection must be made. This is an exception to the above rule, although even here you may benefit if you can find a consistent carrier.

Pick a flight with plenty of seats left

The fewer seats left on a plane, the more expensive they are. Seats in a flight are portioned in groups called "classes". Each class has a price. The cheapest classes sell first.

Avoid holidays

Traveling during the holidays is notoriously expensive. Most airlines have black-out days around popular holidays. Not only are the fares more expensive, but often you cannot use frequent flyer points during these periods either. Ironically, the day of the actual holiday is commonly not a black-out day and seats are often available right up to the last minute. Flying on the day of a major holiday can sometimes be a way around poor availability and expensive fares.