Choosing the right ATV/Motocross helmet for your riding style is an intensely personal decision. Most helmets made today are constructed using lightweight, space-age materials and are DOT (Department Of Transportation) approved.
A helmet for riding motocross and ATV is the first and most important piece of safety gear you should buy. Motocross and dirt bike helmets are normally designed to be both lighter weight and durable. They usually have full face protection because of the flying debris and rocks ("roost") that gets kicked up during a ride.
ATV helmets are made from durable injection molded plastics and in case of an impact, will offer you unrivaled protection. Most come with full face protection as just as much debris can get kicked around by an ATV as a dirt bike. Most have venting systems to keep you cool and contrary to popular belief, you can actually hear BETTER when you wear a helmet no matter if you ride an ATV or a dirt bike because the wind noise is reduced in your ears.
Make sure your helmet is DOT certified and most of all, try on a helmet before you buy it. Make sure it's not too heavy and fits correctly. A helmet should fit snugly but not constrict your head and it should go on and off with little resistance.
Last but not least, the look of your helmet is again up to you. There are low-key solid color helmets and there are multi-color helmets that are as bright as can be. You can not only be safe, but truly express yourself through your helmet!