And plan in advance. The more lead time you have, the more options you have. But you may not know it's best to avoid non-stop flights or to take connecting flights. It'll take longer but it can cost less. And if you can, choose smaller, secondary airports.
Fares there are often lower.
So try to fly early in the morning, before back-ups start. And when making a reservation, ask for the on-time record of your flight. Airlines are required to give it to you if you request it. It can be confusing. With most major airlines you must be at the gate 20 minutes ahead of time to keep your seat assignment and 10 minutes to hold your reservation.