Buying ski boots that fit well can be the hardest part of skiing. Think about it: you’re jamming 100 muscles, 26 bones, 33 joints, and a whole bunch of tendons, ligaments, and nerves into a rigid plastic shell with a liner that needs to be broken in or heated and fit to your foot to feel good.

To ski well, you need all of those parts to flex and move. A well-fitting boot won’t constrain your foot’s natural function and it will put you in a neutral position on the snow, a position that let’s you feel and respond to what’s going on underneath your skis.

Some master boot fitters, including Jeff “Ernie” Ernst, 29-year boot fitting veteran and owner of Park City, Utah’s Bootworks, say that any skier—from beginner to expert—will be better off in custom boots. Steve Cohen, founder of America’s Best Bootfitters and CEO of Masterfit University, thinks that stock boots will work for most people. But both agree on this point: getting set up properly by a trained fitter in a boot that roughly mimics your foot shape on an insole that supports it will result in endless days of shredding without foot, knee, or back pain.

"When you're buying ski boots, you’re not just buying a product, you’re buying the service that goes with it," says Cohen. "And that service will make the difference between a great day, week, or season on the slopes, and a ski season you’d rather forget."

Buying new boots or ready to get the ones you already own to work? Here are some options for setting yourself up for your best performance on snow.

CHOOSE A GOOD SHOP AND A FITTER YOU TRUST
“Choose a boot fitter who has been at this for a while,” advises Cohen. “Boot fitting is part heart and part science, but not a lot of mystery. If you go into a store and they ask you what size you wear, walk out.” “Avoid sporting goods stores when you’re buying boots,” agrees Ernie. “Find a specialty retailer or boot fitter with one or more experienced technicians on staff. You’ll have more fun skiing, and in the long term it’ll save you money.” Cost: free.

GET IN THE RIGHT BOOT SHELL SIZE
“Have a boot fitter, not a sporting goods store, evaluate your shell—if you’re not in a boot that’s the right size for your foot and the right shape for your foot, nothing else will help,” warns Ernie. To correctly size a ski boot shell, a boot fitter will first measure the width and length of each foot. He’ll evaluate your instep height and your heel and forefoot width as well as your shin diameter. Then, he will remove the liner from your boot and check how much space you have when you stand barefoot in the liner-free shell with your toes lightly brushing the front of the boot. He’ll measure behind your heel for a finger to finger and a half (3/4 inch to an inch) of space. Cost: free.

BUY A SUPPORTIVE FOOTBED
“Any good boot fitter won’t do anything to your boot or liner until he has your foot stabilized,” says Cohen. “And 90 percent of fit issues can be solved with a supportive insole. It’s like building a good house in some respects—the foundation matters.”