Your feet should be about shoulder-width apart, in order to allow a balanced distribution of weight. I like to put 55 - 60 percent of my weight on my lead leg, so that its easier to move forward. Keep your knees bent, and be on the ball of your rear foot.
Erm, what style are you? Because if you're a thai boxer, then your stance is completely lobsided. I put 60 percent of my weight on my rear leg, and always be on the ball of my lead leg. This way you can block kicks easier, step out of the way of kicks easier, and put more power into your punches and kicks.