Here’s a scenario that might sound familiar: That conference of yours is creeping up on you, and you haven’t booked travel yet. Suddenly, you’re on the hook for some big charges.

How can you make sure this scenario never happens again? Consider these tips from travel professionals to make booking your next trip a bit less painful:

When to book? Depends on the destination: According to a recent study by Kayak.com, for U.S. domestic travel, booking three to seven weeks ahead is generally best, but the destination matters a lot when booking an international flight. While you generally can book a flight to an African country about a month in advance and get a cheap fare, the lead time is closer two months to most European countries and about six months for a flight to South Africa. But if you’re flying to Asia, you should probably book at least nine months out to get a decent price. One thing that the company says doesn’t affect flight prices? “Contrary to urban legend, the day of the week you book doesn’t make a difference in what you pay,” the company writes. “In other words, there’s no noticeable difference between booking on a Tuesday or a Saturday, or any other day.”

Don’t book too early: While not everyone agrees with Kayak’s assessment of booking based on the day of the week, plenty agree with that company’s assessment that timing matters. CBS News Travel Editor Peter Greenberg, writing for LinkedIn, says that there’s just as much of a downside to booking too early as there to waiting too long. “The number one mistake I see most travelers make is to book too early,” Greenberg writes. “Unless you are planning travel for high-traffic days, like Christmas or July 4, you stand the best chance for the lowest possible fare 45 days out for domestic travel and 60 days out for international.”

Flexibility preferred: If you can show up for that conference a couple of days early, there’s a good chance you can save big, according to Telegraph Travel Consumer Editor Nick Trend. “The best advice for when to book flights depends both on when you want to travel, and how flexible you are able to be,” Trend says in an article for the British site. “If you are a family who wants to fly during the school summer holidays on a particular date, you should certainly book now. If you leave it later there is a very high risk you will pay a much higher fare, and may not even be able to book the flights you want at all.” Telegraph Travel notes a general rule of thumb: When there are higher levels of seat availability, you can get a cheaper ticket.

If you’re reading this site, there’s a good chance you’re a frequent flyer. Do you have travel tips you’d like to share? Offer them up in the comments below.

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