Well walking the circle is crucial for helping you develop the necessary power for utilizing your attacks. However it is not directly related to the system of reaction regarding combat. There are other steps that can be used leading to thousands of modifications, but the beginning step is easy enough to explain. Stand so that most of your weight is on the back leg. The front leg should be about a shoulders length apart (roughly) and light, ready to move in either direction. It shouldn't be too light however because you may have to use it to move backwards. Remember when moving forwards, the lead leg should raise while pushing from the rear. When moving backwards the back leg should raise first while the front leg pushes to the rear. Whether moving forward or backward the legs should adjust to their original spacing, not allowing them to come to close or to far apart. The weight should still remain mostly in the back and the body should not elevate in mid step. If you elevate yourself as your opponent moves in, you will fall to the ground. This is why it is crucial to develop leg strength to maintain a low stance even while moving swiftly in order to place him off-balance if there is an un-forseen collision. Hence lots of circle training.
This would be the way of the legs motion training. Of course the step can be practiced in a half step, full step, Inward step (Kou Bo), outward step (Bai Bu), turning step, crossing step, leaping step, sinking step, angular step and so forth. But before moving to other steps make sure that you can use this single half step effectively. So when you push off from the back leg, make sure it doesn't come to the front, that would be a full step. Practice this step both forward and backward and get an idea of the rhythm of your feet. Once it gets easy begin thinking about attacking and defending.
All of the energy must be drawn from the back leg and then taken through the hips. The hips regenerate the energy through out the rest of the body with a flowing motion. The body holds the structure of the attack through the muscles in the back allowing the hands to relax while firing the attack. Much like a circuit, if there is any problem with the connection to the ground there will be no power. Also if you tighten up and put a clamp in the connection, you will lose all of your force. So only by remaining in a structured position while staying relaxed can one begin to draw internal energy.
While doing this step it's easiest to use the single palm strike. When you step forward allow the hand to fly straight fired off the hips. The legs pull the body and the body pulls the hands, meaning the last thing to move is your hand. If your hand moves before your step takes place, you will lack power. Take your time learning your timing. Even the masters have been working the same step for decades so it can always get better. You can also use the same attack while stepping back, full step, turning step, leaping step and....I'm sure you get it by now. The lower you remain to the ground, the more power you can attain. However it is essential to remain swift from a deeper stance. So have a friend try to punch you in the face.....careful though. Thanks for the question Kyle, you gave me a good blog.