One of the basic "rules" of karate seems to be that if you are comfortable then your stance is probably wrong. Of course, if you are not comfortable that doesn’t mean that your stance is right. So how do you tell if your stance is right or not?
Stances are based on your own body size and may be often referred to in relation to your shoulder width, leg length etc. Assuming that you practice at home this means you could measure and mark out an area of ground with the foot positions which are right for you.
Once you get used to stepping out onto the marks you have made and can remember the "feel" of the stance it will make it easier to get your stance right when you are at class and don't have these marks to help you set your stances.
If you have a large enough area at home you could even mark out where to put your feet for the kata you are working on. Although it is usually best to do this sort of thing outside where you are less likely to get in trouble from the boss of the house!
Remember, the best way to improve your karate is practice, practice, practice!
- Mick Todd