Stand with your feet spaced at hip width and place your hands on your hips.
Start by taking a large step forward with one leg. Bend until your front leg makes a 90 degree angle and your back knee almost reaches the floor. Then drive through your front foot to extend the knee, returning to a standing position. Keep the majority of your weight focused on the front foot as you lower your hips down and bend your front leg. Your front foot should remain flat as you lunge but your back foot's heel will lift off the ground. Repeat for the desired amount of repetitions.
Avoid using momentum by using your shoulders to pull back at the bottom of the movement or by bouncing back up.