“When parents start to shop for a two-wheeler, they’ll often ask for one that will last several years, but this doesn’t really exist,” says Jay Tarrant, manager of Sid’s Bikes NYC in Chelsea. Anything too large will be unwieldy and difficult to control. The smart way to shop is to get a little bike for a little kid and then trade up as he grows. Here’s how:

Is he ready? By age four or five, your tot will be able to handle the weight of a heavier, bigger two-wheeler bike. Until then, don’t rush it; let your little guy enjoy his tricycle (see “Joy rides,” page 48), Big Wheel or baby scooter. (Balancing trainer bikes can be used starting at age two.)

Measure well. A 16- or 20-inch bicycle is usually a good fit for first-timers (kids’ bikes are measured by wheel diameter, not frame length); the rider should be able to sit on the seat with his feet flat on the ground, not on his tiptoes.

Keep it simple. Kids under ten don’t need multiple gears. Choose a basic single-speed model, on the heavy side, with solid construction. It’ll likely come with both coaster brakes (the ones that click in when pedaling backward) and hand brakes.

Think locally. Big-box stores sell bikes at lower prices than your neighborhood shop, but you’ll miss out on the personal touch, like free tune-ups and seat-adjustment help. Go for a nearby shop with a wide price range of bikes and a knowledgeable staff (bikes here will run you about $100 to start).