Make sure you try the helmet on for size before purchasing. It should fit securely. It should also have a strong strap and buckle, since the strap has to hold the helmet onto your head if you do fall and hit the ground. For children's helmets, adjustable inner pads can be used to ensure a snug fit that can be adjusted as the child grows. Most of all, if you ever should fall and hit the helmet, replace it at once.
Any impact can crush the protective foam.
Even if it doesn't look damaged, it will still be less able to absorb future impacts. You should also replace a helmet if straps or buckles are worn. The National Highway Traffic Safety Commission also suggests that the bike be checked to make sure it is adjusted properly and that the brakes are functioning correctly. It also urges bright clothing and avoiding riding at night and in wet weather. Parents should also stress all safety rules to their children when they go out riding.