Toes Out, Heels In
We can easily just focus on our hands during Chi Sau, really we should focus more on our legs and this is the key to good Chi Sau. If we watch people doing Chi Sau, but instead of watching their hands you watch their legs, we can see who is good and who is bad.
The Wing Chun stance is called Jih Zih Kim Joeng Maah 二字鉗羊馬. The stance is like a triangle, with the toes pointing in and the heels out and the feet should be shoulder width apart. However, we commonly see people doing Chi Sau with their toes pointing out and their heels in, which is opposite to the teaching of Jih Zih Kim Joeng Maah. Jih Zih Kim Joeng Maah makes us strong, if we are doing it the opposite way will make us weak. During Chi Sau however, our feet are actually parallel, which makes it easier for us to go backwards and forwards, making our footwork more mobile. however if our toes point out and our heels point in this means we cannot move forwards and backwards easily and so standing like this is a very bad habit. we must change this by training our stance and we also need to practice the Seven Star footwork 七星步法 in particular we need to train our Jyun Maah轉馬, Waahng Maah 橫馬, Jeun Maah進馬 , and Teui Maah退馬.