A foundation of Wing Chun is the protection of your body's center line. Imagine a line that starts at the middle top of your head and travels along the middle of your chest to the lower body. This is the center line of your body and it is the most vulnerable. It must be protected at all times.  According to the center line theory, you should always attack down the center line and perform your defensive moves against your opponent’s center line. The basic open stance in Wing Chun is based on the theory of the center line. In the open stance, stand facing forward with your knees bent and your feet pointing slightly outward. By facing your opponent head-on, you are able to attack with the most balanced force. A key Wing Chun principle is that, during fighting, energy should be used conservatively and economically. Use your opponent’s energy by deflecting or redirecting blows.  Use motion economically and wisely. The idea here is that your body should travel the shortest distance in a minimum amount of time to connect with an opponent. This also helps to conserve your own energy. A tense body will use energy unnecessarily. Keep your body relaxed and you will be more at ease. If you have experience in other martial arts, (especially "hard styles"), you will have to "empty your cup" or unlearn bad habits. Wing Chun is a soft style with many neutralizing techniques that require you to be "soft" and relaxed. Reconditioning your muscle memory and building relaxed habits can be frustrating and takes time, but it will be worth it in the long run. In Wing Chun, the fighter will react to a fight using quick reflexes to interrupt an attack and change the fight to be on your terms. Your opponent might be tall or short, big or small, male or female, and so on. Similarly, the environment in which you fight can be different – outside, inside, rainy, hot, cold, and so on. Be ready to adjust your fighting to suit the conditions. The practice of Wing Chun is broken into a succession of six different forms, each of which builds on...

TL;DR in Vietnamese:
Tìm hiểu lý thuyết đường trung tâm. Hãy sử dụng sức lực một cách khôn ngoan và tiết kiệm. Hãy thả lỏng. Rèn luyện phản xạ. Thay đổi chiến thuật theo đối thủ và môi trường. Học các bài quyền của Vịnh Xuân Quyền.