Jump off curbs. Practice riding off sidewalk curbs to get the feel of dropping over obstacles. Jump on curbs. Practice jumping onto curbs to get used to the feeling of jumping over obstacles. Play with your gears. Practice shifting gears and riding up and down hills so you get comfortable knowing when to shift into what gear. Higher = harder/faster. Play with your pedals. If you're using clip-in shoes, practice clipping in and out until you're comfortable with it, both while stopped and while riding. Protect your eyes. Don't forget sunglasses to protect your eyes from wind, dirt and bugs. Stand up. Learn to ride while standing, and try shifting your body towards the back of the bike when you go over obstacles. Wear bike shorts. Bike shorts have padding under your rear end to keep you from getting sore on long rides. You will not be sorry you wore them. Wear gloves. Mountain biking gloves can protect your hands from the tension in your grip, and keep them from getting cut up if you crash. Bring water. Bring water bottles or a hydration pack to stay hydrated when you're biking. Clip-in shoes. Clip-in shoes can make your ride more efficient because they leverage the force of your upward motion. Make sure the shoes match your pedals.