Roundhouse kick:
Stand with the right side of your body facing an imaginary target with your knees bent and your feet shoulders' width apart. Lift your right knee, pointing it just to the right of the target and pivoting your body toward the same direction. Kick with your right leg, as though you are hitting the target. Repeat with your other leg.
Front kick:
Stand with feet shoulders' width apart and arms at a 90-degree angle in front of your shoulders. Bend your knees slightly, and pull your right knee up to your chest. Point your knee in the direction of an imaginary target. Then, kick out with the ball of your foot. Repeat with your other leg.
Side kick:
Start with the right side of your body facing a target. Pull your right knee up to your left shoulder, and bend your knees slightly as you kick in the direction of your target. The outside of your foot or heel should be the part that would hit the target. Repeat with your other leg.