Adjust the chin clip so that it rests in the middle of your chin, leaving only enough room to fit one finger between it and your chin. When you open your mouth wide, the strap should pull the helmet down on your head. If it doesn't, tighten the strap. The side of each strap should form a triangle around your ear with one point meeting right below your ears. Try pushing the helmet from both the front and the back. If it tilts more than an inch, tighten the straps to provide a closer fit.