Johnny Jet says that it's a good idea to sign up for fare alerts with all your favorite airlines and to use Google Flights to see how often the prices change. Don't buy too far in advance, but don't buy at the last minute either. You usually want to book between 14 and 21 days in advance. You should also look at alternate airports. Often you can save over a hundred dollars or more by going with an alternate airport. Add a stop, too. Sometimes there is a huge difference on a one stop flight, especially if you're flying as a family. You won't be able to book Southwest on Google Flights, but that airline gives you two checked bags, so you can save a ton in baggage fees.