Tip #1: Make your reservation early.
Many discount fares require that you make a reservation 7, 14 or 21 days in advance, depending on the fare. The best international fares often require a reservation 30 days in advance. Making a reservation as soon as you know your travel dates increases your chances of finding a great fare.
Tip #2: Flying on a weekday usually costs less.
Flights departing on Tuesday, Wednesday and Thursday usually offer the lowest fares. Fares are sometimes (but not always) higher on Monday and Friday than on other weekdays. Saturday flights occasionally have discount fares, but as a rule it's more expensive to fly on a weekend than a weekday.
Tip #3: Stay over a Saturday night
Most low fares require that you stay over at least one Saturday night before your return flight. However, some fares may only require you to stay a minimum of 3 or 4 days.
Tip #4: Consider an airport in the surrounding area.
You may enjoy significant savings if you are willing to fly into nearby airports. For example, when traveling to Amsterdam, you may want to consider flying into the Dusseldorf, Eindhoven or Brussels airports. Similarly, the cost of a trip to San Francisco might be reduced by flying into San Jose or Oakland, while travel to Miami may be less expensive if you fly into Ft. Lauderdale.
Tip #5: Try an earlier or later travel date.
To get the lowest roundtrip fare, the same fare must be available on both the departing and return flights you select. If the fare is sold out on either of these, the price you end up with will be much higher. If possible, consider flying on another date.
Tip #6: Book round-night flights.
Fly early mornings or late evenings; these are less busy and often can be less expensive.
Tip #7: Use the same airline for your rount-trip.
Stay with the same airline during your entire trip to receive round-trip or connecting fare discounts.