Come fall, everyone seems to get all amped up about buying the lightest and sexiest pair of new touring skis. But experienced backcountry skiers know that the single most important piece of gear you own—especially when it comes to touring—is your boots.

“It’s like having the right tires to drive on the snow,” said Mark Elling, bootfitter at Mt. Bachelor’s Gravity Sports, curriculum director of Masterfit University (MFU) and staff manager of the MFU bootfitting workshops. (He’s also a former board-certified pedorthist, an author on ski technique, and level III PSIA Alpine Instructor.) “Your life depends on them, ultimately, because that’s what controls your skis.”

Here are some tips from Elling on how to buy them.

• Do not buy boots online (unless you’ve tried on that exact model and size in-person). Go to a brick-and-mortar store and work with someone who knows boots. Preferably it should be a specialty backcountry-skiing store.
• Buying boots is like any relationship—whether you’re buying a car or equipment or dating, the person you’re dealing with should be some amount of interest in you and your goals. It all starts with conversation, and it should feel as though you are the focus.
• The shop person should look at your foot and leg and measure you without shoes on. “No good bootfitter is going to believe you about what size you are until they check you on a measuring device. They’re also looking at whether your foot is narrow, medium, or wide,” Elling says.
• After doing an analysis of your feet, ability level, and goals, the bootfitter will likely bring you several pairs of boots to try. What people perceive to be a comfortable ski boot can vary widely depending on experience, ability level, or tolerance for compression. New ski boots should feel a little too snug, like a very firm handshake. If you go too big for comfort, you will end up cranking the buckles too tight when the boot breaks in, which distorts the boot shape and creates other problems. Another common issue with too-big boots is your heel won’t stay in the heel pocket and your toes will slam into the front. “You need a fitted boot to keep your toes from sliding forward. There are 10 different ways a bootfitter can make more room for your toes, which is a better way to go than going up a size,” Elling says.
• The key points of fit are going to be your instep, which is what holds your heel in the pocket of the boot, and your shin. Your instep should feel snug and comfortable, and you shouldn’t feel sharp pressure points. The pressure on your shin should be evenly distributed, and you should have a progressive flex with no shelf or breakover point. “If those spots feel good, almost everything else is workable with a good bootfitter. But even the best bootfitter can’t fix a bad fit in those two spots.”
• As far as flex goes, the stiffness you need depends on your weight, height, and ability level. However, the flex you get will also depend on your backcountry objectives, i.e., how heavy you’re willing to go. All backcountry boots inevitably feel less stiff than their resort counterparts, because there is simply less plastic to mash your shin into.

Regardless, Elling said when you press your shin against it, the boot should prompt you into a skiing stance that you can relax against. If the boot is too soft, you’ll feel like you’re doing a wall sit and your quads will be tired. Another sign a boot is too soft is if the lower boot bulges as the upper boot collides into it.

A boot that is too stiff, on the other hand, won’t let your ankle bend properly, which means your knee and hip won’t follow suit. “Then the only flexion that occurs is your ass going into the backseat,” Elling said. “You have to have true ankle flexion to ski well.” You want a boot that allows you to flex the upper cuff. If you don’t see the upper cuff move relative to the lower boot, that’s too stiff. Also, keep in mind that boots will be softer in a warm shop; they stiffen up in the cold. When in doubt, choose the stronger flex. “If it’s a little too stiff, a good bootfitter can make it softer. But you can’t go the other way.”

• When it comes to backcountry boots, it’s good to keep your fiddle-factor low. The more bells and whistles it comes with, the more chances there are for shit to go wrong. And when you’re in the wilderness, well, you want shit to go right.
• When it comes to insoles, Elling said you should replace the ones that come with the boot with either an off-the rack insole or a custom one. “Most people get improvement in comfort and performance, regardless of their skill. The off-the-rack insole is made for average Joe, so if you have low or high arch, those may not be the best solution. People who have nonaverage feet, who are looking for true performance or balance advantage, or those who are knock-kneed or bow-legged should get custom insoles.” Custom insoles last for longer, too, so they’re worth the investment.
• Socks are super important. If your boot is new, start with a thinner sock. Over time, when it packs out, you can get a thicker one to take up volume. Elling recommends a new pair of socks for each day on a ski trip, because when they get clogged with sweat, they’re not as warm. (These Dissent Labs ski socks are worth it. Trust us.)
• Keep your boots dry. Most serious skiers have boot dryers. Dry boots last longer, because the liners will re-loft, and they won’t smell bad.

Overall, Elling said that the most important thing about buying new boots is that they don’t have to be perfect out of the box. They’ll get more comfortable the more you skin and ski in them, and bootfitters can do wonders.