How to wheelie:
make sure your back brake is not just working, but working really well. You can help yourself by adjusting your saddle to a middle position, which will keep your center of gravity lower and help with your balance.
Make sure you use a low or lower gear, the lower the better. Begin at a slow or rolling speed and keep your weight central.
Turn your cranks and position your pedals to the 2 o’clock position. Push down hard on the pedal and simultaneously pull up on the handle bars. It will take a few attempts to find out how quickly and easy the front end comes up.
Start off cautiously. As you get better get closer to that balance point. You are trying to lift the front wheel to a point where it takes the minimum effort to stay balanced on the rear wheel. Once you find this balance point, the back brake is your friend. Pull it full and it will stop your back wheel dead. The aim is to find the balance point and keep it by dabbing the rear brake and pedaling harder.
Once rear balance is in control, work on side balance. Use your knees, feet, and body weight. Turn the handle bars in opposite directions.