Much of the advice a student receives seems contradictory. However, it is usually just a matter of knowing under which circumstances the advice applies.
Some Wing Chun schools say to always apply the slapping hand to the elbow or else you will lose. Others apply it at the wrist. However, every application of a movement has its pros and cons. The use of a particular movement often depends on the circumstance. Applying the wrist slap you gain more leverage, and you keep further away from the opponent, but you must also be ready for the opponent's arm to collapse into an elbow strike. Applying the elbow slap avoids this elbow attack, however, a smaller person may not be able to reach or to compress the opponent's elbow.
Beginners often move their stance too much. Every hand technique is preceded by a telegraphing movement from the stance, thus, the techniques are always too slow. Weak stances cause beginners to be easily off balanced by their opponents. It also reduces the force of the beginner's attacks.
In Wing Chun, you learn to use your body structure to its maximum force receiving capability. If the force is still excessive, the stance gives way. The collapse often happens so rapidly that the opponent is thrown off balance for a short duration. This gives you a chance for attack.
When the beginner is taught the Chum sau in the single sticking hand exercise, he is instructed to use only the wrist action. Instead he often uses the crude action of pushing down stiffly with the whole arm, and therefore, is not learning to use the force of the wrist. Once you are able to generate force from the wrist joint, only then do you add more joints to increase force.
There is always a balance between practice and theory. Too little of either doesn't produce the intended result. Beginners often ask questions which are beyond the level of what they are learning. They want to know how they can beat a boxer, a wrestler, a Karate expert, etc. They want to know everything except what they are supposed to learn. Instead of using their own minds to analyze the problem, they ask what to do every time they are stuck. This kind of questioning is a waste of time.
On the other hand, a student that asks no questions may be showing that he is not bright enough to comprehend what is being taught. Some instructors will only give you the information that you ask for.
Wing Chun divides the arm into three stages; the hand to the wrist is the first stage, the wrist to the elbow is the second stage, and the elbow to the shoulder is the third stage. The saying, "Don't let the opponent past the first stage of the hand," means once the opponent enters past the first stage, you must attack or retreat. The use of this principle prevents non-stoppable critical distance hits, and gives room to maneuver by not letting the opponent's hand closer in than your extended wrist. Once you attack how- ever you get in as close as possible and use your full array of techniques. They say attack the opponent through the second stage. When you attack, try to control the opponent's arm (near his elbow) for as long as possible. This reduces his chances for counter-attack.