Number one on the list for safety gear, and for more reasons than you might think. Nearly every state has a law in place requiring that all riders wear a helmet—and not just any helmet. When shopping, look for the “DOT” and “Snell” logos on the back of the helmet, which mean the helmet passed a high level of safety standards that are approved by state and federal authorities.
Your helmet should fit snugly and fasten securely. Full-face helmets protect the face and head, while open-face models are lighter and cooler for hot summer months. Either way, make sure there is no obstruction of vision, including peripheral, so you can see any danger approaching from either side of the vehicle.
Above all else, the first thing you should put on is the helmet. Make it as routine as fastening the seat belt in your vehicle. The only time not to wear a helmet is when stopping to talk with landowners or others you meet on the trails. To some people, your helmet is a mask and can be intimidating.