When you first start working out, it’s tempting to dust off the vaguely-athletic-looking shoes in your closet, but it’s not a good idea. Worn-out or ill-fitting shoes are a leading cause of injury. And wear and tear are not always apparent to the naked eye. If you want to stay healthy, fit, and injury-free, invest in a good pair of running shoes.

Follow these tips to make sure you get the pair that you need.

Don't skimp. It may feel like a lot to spend up to $120 on a pair of running shoes, but the investment is worth it. Consider this: Whatever your new shoes cost, it is likely less than the money and time you’d spend seeing the doctor because you got hurt.

See the experts. It’s best to go to a specialty running shop (not a big-box or department store) where a salesperson can assess your gait and watch you run and help you select a pair of shoes that offer your feet the support they need. Find a specialty running store near you.

Size yourself up. You may think you know your size, but it’s best to get your feet measured each time you buy new shoes. Your feet change over time, and one model’s fit can be drastically different from another’s. You also want to have your fet measured later in the day, when they're at their biggest. Many people end up getting a running shoe that’s a half size larger than their street shoes. The extra room allows your foot to flex and your toes to move forward with each stride. When you’re standing with both shoes on, make sure you have at least a thumbnail’s space between the tip of the shoe and the end of your longest toe. Try shoes on both feet and take them for a test run around the shop, on a treadmill, or on the sidewalk.

Bring what you’ve been wearing. When you go shopping, take along the shoes, socks, and any inserts that you’ve been using. That way you can make a realistic evaluation of how well the new shoe will fit your feet.

Keep up the rotation. Shoes should be replaced every 300 to 500 miles. Keep track of the date that you bought them in your training log.

Don’t be a trendsetter. There is a dizzying array of shoes to choose from, and it can be tempting to be wooed by a bargain-basement price, shoes that “look fast,” or a promise to cure an injury or help you lose weight. But there is no one best shoe for anyone. There is only one shoe that offers your feet the unique support and fit you need. Try on as many different models and pairs as possible. Don’t shop by price or by fashion. And what about those minimalist shoes designed to mimic barefoot running? There’s no scientific evidence that forgoing shoes decreases injury risk. When you’re just starting out, stick with traditional shoes.