In the image I have provided you can see the proper form of a classic round house kick. To start simply raise your knee up to your torso. As you kick twist your hips and unleash your attack. Be certain to have enough control not to pass the center of your body. It is important to bring your leg back in and return to your original stance after this or any other kick. This insures a safe finish in case you miss.
A side kick is simallar to the round house. First start by raising your knee to your torso and then twist 90 degrees lifting your foot up to your knee. Stike using the ball of your foot then return to the twisted raised knee position. Twist back into the standard raised knee position and then return to your standard position.
Next is the standard front kick. Like with the round house lift your knee to your torso then perform your kick. Try and hit with the ball of your foot. Once you have completed the kick bring your leg in and return to your stance.
A crescent kick is much like the front kick and is useful for disarming opponents or surprising them. Bring up your knee and arc your kick either inward or outward depending on the situation. After completing the kick you should be in the standing position with your knee raised to your torso. From this you can kick again or return to your stance.
The windmil kick is a little more difficult and less likely to see combat for beginers. Using your front foot twist around raising the other knee. As you return to facing your opponent unleash your kick. Do not cross over the center of your body. Once completed return to the position of one raised knee and then again to the starting position.
Finally we have reached the back kick. Raise your knee as you would for any other kick and then begin to crouch forward. Unlease your kick while maintaining your balance. Then return to your starting stance.
As you practice these kicks always start by lifting the attacking leg into the raised knee position. From there try to mix it up, you may need to change a kick in an instant so it makes for good practice. Also practice spinning 90 degrees from that stance to change directions. It seems silly but comes in handy and can be a real game changer.