All footwork is initiated from a guard position (fighting stance). There are many guard variations, choose one that is effective for you and that your are conformable using so you are not tense and may react instantly. The guard should have your strong side forward, hands up near cheek bones, with elbows tucked in. Lead shoulder slightly raised and chin tucked. Lead knee turned slightly inward to defend groin area. Both heels slightly raised for quick movement. Both knees bent as much as possible while still permitting smooth, quick movement. Bent knees permit quick jumping without have to telegraph a jump by first bending the knees.
Footwork in not merely bouncing or rapidly shifting stances. It is simple, natural movements that permit quick but smooth changes in direction or range. Footwork should enhance your body alignment and stability so you may deliver powerful block and attacks. Footwork allows you to lure your opponent into an attack or counter attack. Use it to setup your opponent and yourself for attacks. Footwork is not just for moving, it is also the delivery system that allows you to execute your techniques properly. Any properly executed kick or punch comes off the footwork.
All footwork starts with your basic fighting stance. Whatever stance you use, it must be stable and permit blocks and attacks by hands and feet, and you must feel natural and relaxed while using it. A common fighting stance has strong side forward, both fists just under the eyes (to protect face) with elbows tucked in (to protect midsection), lead shoulder raised a little with chin slightly tucked behind the shoulder (to protect chin), and lead knee turned slightly inward (to protect groin).