Dynamically shifting your bodyweight from the rear of the bike to the front allows you to unweight the rear wheel. This can be the key to keeping the flow on rough technical trail or clearing rocks. This is important to master, and will help with your bunny hop too.
1. Hips Back - Shift your hips back and down to load the back of your bike. Doing this should increase the pressure on your pedals. Then throw your hips towards the bars. Push back against your pedals, with your toes pointing down.
2. Weight Up Front - As the rear wheels comes up, allow your weight to come into your hands. The bike is pivoting over the front wheel so you should feel your bodyweight in front of that balance point. Move your weight back again to drop the wheel.
3. Head up - Once you've acknowledge the obstacle, look where you want to go, keeping your head up and eyes looking down the trail. Don't look at the floor in front of you - this can have the adverse effect of pivoting you straight over the bars!