New folks tend to try and kick with only their feet, using only their leg. Like a punch, one should use one's body to start the motion. Whip one's shoulders, waist, and hips over. That should get the momentum going. Then the leg will follow with little effort. Start with low round kicks at a knee target. Once the form is perfected, kick at the rib cage target. Once one is completely warmed, kick at a head target. They all use the same basic mechanics, just at different levels.