Whatever type of shoe you’re buying, they can affect the health of your feet — and far more. "If your shoes aren’t absorbing shock well, then your feet will, and then your knees, hips and back," says Dr. Jacqueline Sutera, a podiatric medicine and surgery specialist in New York City. Some tips:

Consider the activity. Running and walking shoes are designed for forward motion, while tennis, basketball and cross-training types are meant to move from side to side.

Go shopping late in the day. Your feet are smallest in the morning, before swelling and gravity do their work. Your shoes should fit the bigger size.

Don’t be too loyal to your size "number." Not every shoe company cuts its products the same way. Your size should be a starting point only; the best fit may be a half- or even full-size away from usual.

Fit for your longest toe. Don’t focus only on the "big" toe if your second toe is actually longer. Aim for about a thumb-width of distance between your longest toe and the end of a shoe.

Don’t buy flip-flops as walking shoes. Flat, cheap flip-flops don’t offer enough support for anything but short distances; thongs also force toes to over-grip to hold shoes in place. Overuse can cause serious injuries, including fractured bones.

Invest in sturdier sandals for walking. Look for a thicker rubber bottom than most flip-flops have — about ¾ of an inch — along with straps and some arch support.

Buy alternatives to heels. Any heel higher than two inches can cause problems, but if you do wear one, keep comfortable flats handy to give your feet some breaks during the day. Don’t wear the same height heel every day of the week, which can damage tendons.