Recently, I was talking to a friend who was planning a trip later this summer to Naples, Italy. He asked for my advice on how to find the cheapest flight. I have a whole 17-step guide, which you can read here, but I need to update it with this new tip.

First of all, to find the best deal, you need to be flexible in every aspect, especially when it comes to travel dates and alternate airports. However, there’s one strategy I don’t think I’ve ever mentioned—except last week, when I wrote a tip about the cheapest days to travel this summer, according to Expedia data. Instead of picking a destination first and then searching for flights, many savvy travelers let airfare deals determine where they go.

This is important because it’s a great way to save a boatload of money, and there are a variety of ways to go about it:

1. Sign up for flight deals

There are multiple sites that flag airfare deals, but to get the really good ones, you usually have to upgrade to a premium membership, which comes with a subscription fee. Is it worth it? It depends on how much you travel and how big your trip is going to be. If you’re flying economy once a year on a domestic trip, I’d probably pass and save the money. However, if you travel frequently, want to take an epic international trip, or prefer flying in the front of the cabin, then paying for one or more of these services can easily pay for itself—and then some.

Here are some companies that offer both free and paid flight deal subscriptions:

Going.com

Going.com is a flight deals service that monitors airfare from U.S. departure airports and alerts members to exceptional fare drops, mistake fares, and points deals. They help travelers book directly with airlines at significantly reduced prices. In just the past week, they’ve emailed me round-trip deals from the U.S. to Malta for $711 in August. Yesterday, they also alerted members to Hawaii fares ranging from $202 to $293 round-trip for travel between July and December.

Dollar Flight Club

Dollar Flight Club is a flight deal subscription service that searches for discounted domestic and international airfares, including mistake fares, and sends personalized email and SMS alerts based on your preferred departure airports and destinations. It helps travelers save on flights without constantly monitoring prices themselves. Recently, they sent me deals including Los Angeles to Salt Lake City for $79–$145 in economy and Los Angeles to São Paulo, Brazil, for $485–$539.

Thrifty Traveler Premium

Thrifty Traveler Premium is a subscription flight deal service that sends personalized alerts for deeply discounted cash fares, award flights, and premium-cabin deals from your preferred departure airports. It helps members save money—or points—on domestic and international travel. Just yesterday, they emailed me a deal from LAX to Tahiti for 60,000 points each way (nonstop summer flights that normally cost more than $3,000).

In fact, it was Thrifty Traveler Premium that made me realize I’d never written about the “Flight First Rule.” As they wrote in their newsletter: “Most travelers do it backwards—they lock in hotels or other nonrefundable parts of their trip first, then start searching for flights. The problem? That kills flexibility and usually makes flights way more expensive.

Instead, start with the flight deal. When you spot an amazing fare, book it first, then figure out the rest later. Flights are often the biggest cost of a trip, and locking them in early leaves more room in your budget for everything else.”

So the next time you’re looking to save money, think of the Flight First Rule.

2. Use Google Flights Explore

If you have specific dates in mind but are open to going anywhere, definitely use Google Flights’ Explore feature. You can enter your departure city and leave the destination field blank, or enter a country or even an entire continent to browse options. You can search using specific dates or make them flexible by month, week, or even weekend. See the screenshot above.

3. Set fare alerts

If you have a specific trip—and dates—in mind, set a fare alert using Google Flights or Kayak. Here’s more information on how to do it. I even set fare alerts after booking a flight on a major U.S. carrier because if the price drops, I can cancel and rebook to receive a travel credit, as long as I didn’t book a Basic Economy ticket.

I also use TripIt Pro for this very reason because they do an excellent job of notifying members when they’re eligible for a credit. See the example of an alert I recently received.

Hopefully, these tips and tricks will help you save money and explore more of the world.