If you’re a true adventurer, you’re likely already saving up for your next trip. After all, 76% of millennials would rather spend their money on experiences — like travel — than on material things. That said, it’s likely you don’t want to pay more than necessary for an airline flight. When you look up available ticket prices and spot what you think might be a great airline deal, the eternal question is: “should I wait or should I book?” The tips outlined in this guide should provide some answers.

Know Your Prime Buying Window

Believe it or not, there is a science to discount travel. Well, sort of. Buying too early might allow you to choose any seat you want on a plane, but you’ll pay a lot more for the privilege. But booking at the last minute will actually cost you a lot, too. According to the Airlines Reporting Corporation (ARC), the lowest airline ticket prices can usually be found 30 days before departure. If you buy them too far in advance or wait too long, you might miss out on a great ticket price. There might not be much you can do if you’ve waited too long (other than to delay your vacation). However, if you’re looking at airline tickets a year in advance, you’ll probably want to hold off.

Know When to Take the Deal

Like a good card player, you’ve got to know when to hold or play your hand. You might not win the most every time, but you’ve probably got a good shot at not losing it all. In the same vein, you should learn to recognize a great airline deal when you see one. That comes with experience and a dedication to price comparison. If you see an available ticket price that, in your gut, feels like the lowest it could possibly get — don’t wait. It’s probably only going to increase from there, so don’t bet on seeing how low it can go.

Know Which Resources to Use

Although there are ways to guess when budget travel tickets will pop up, it’s hard to know for sure — particularly if you don’t have help. There are plenty of resources available that can alert you when a new deal has become available or that can give you a good guess as to whether an airfare price may drop in the future. A lot of these websites (including ours!) and apps are free to use and will give you the best shot at finding a great price for the trip of your dreams. When hunting for travel deals, you don’t have to go it alone.

You may never feel 100% sure when you buy an airline ticket that you’re getting the best deal possible. That’s simply the way it is, even for the most seasoned of budget-conscious travelers. But by utilizing these tips, you should feel fairly confident in your choice to either buy right away or wait for a more appealing price to emerge.