tae-kwon-do master will determine if you are ready to break a board.
For this basic move, believe it or not, 4 positions. Firstly, stand in front of the computer. Now spread your feet one shoulder width apart. Now slide your left foot back 1 1/2 shoulder widths long. (Just in case you can't figure this out yourself, a shoulder width is the length between your two shoulders.) Bend your front leg slightly, and point the foot straight foreward. Straighten your back leg and turn your foot 45 degrees outwards. This is the first movement I mentioned: a Walking Stance.
Now you have to learn how to make a proper fist: make a thumbs-up sign. Then, holding the position, bend your thumb as close to a 90 degree angle you can. Keep your thumb in that position, and slide it over your hand. This type of fist takes some getting used too, but it is a proper fist. Curl both hands into a fist, and move on to the next position.
This position uses both of the other positions already described. Nearing the end of the instructions for a Basic Punch, you now will learn a Guarding Block. You know how a mummy looks, right? Well, place your hands like a mummy, crossed over your chest. Your right hand must be on the outside. Pretend your right arm- from shoulder to elbow- is paralized. Unfold the rest of your right arm, so your arm is close to the classic bicep-showing-off position, except the arm is lower down. Move your left hand 15cm away from your chest, and the rest of your arm will naturaly unfold to the fight postion. This is the Guarding Block. Stay in this position and move on to the last step: punching.
Straighten out your right arm. Now fold it back to a Guarding Block position. Practice this until it comes naturaly. Now add some speed to it. Make sure you are keeping your hand in a proper fist and are not throwing your left arm out for balance. Practice a bit more, and add full power. You have learned a punch.