1. Be Flexible
Search for flight deals a month in advance, and, unless you can fly at a moment's notice and find a last-minute sale, book 21 days out. Avoid flying on Monday, Friday and Sunday, which are generally the most expensive days. You can also save a lot by flying at night (yes, the dreaded red-eye) or early in the morning (like when it's still dark). Try to stay over at least one Saturday to save even more. And travel off-season: everyone wants to fly to Hawaii in winter when it's cold or in summer when school is out, but in spring or fall, those seats are cheaper. Finally, research when to buy airline tickets for holiday travel carefully. In general, the closer to a holiday you fly, the higher the prices — unless, perhaps, you travel on the holiday itself.
2. Alter Your Route
Nonstop flights, although convenient, are expensive. To save money, book a flight with at least one stop. Also, search for flight deals at airports close to your destination. Sometimes it's cheaper to fly into Oakland than San Francisco, say, or Newark instead of JFK. Of course, be sure to factor in any additional ground-transportation costs involved in reaching your final destination.