You want the helmet to be level on the head, not tilted back or sideways.
You want the strap to be comfortably snug.
With the strap fastened you should not be able to get the helmet off with any combination of twisting or tugging.
The helmet should not bump on your glasses or sunglasses in the front.
The helmet should be comfortable enough to forget that it is on your head after only a few minutes.
It will take you more fiddling time then you expect to get it this way.
Replace any helmet if you crash. Impact crushes some of the foam, although the damage may not be visible. Inspect the helmet for any marks, dents, or foam crush to know if you hit. It is recommended that a helmet should be replaced every five years.
Presented by the Bicycle Helmet Safety Institute. A consumer-funded program of the Washington Area Bicyclist Association. www.helmets.org
ALL children, and sometimes adults, MUST WEAR a bicycle helmet. It's A Law.