Unless you have already won, things are changing rapidly either to your advantage, or against. In other words, there is some motion in the system, either from you, or from your opponent, (it does not matter which) but seeing as your opponent's plan probably involves you staying where you are, or moving predictably ... best not do those.
So the goal becomes .... move towards your advantage.
Which in turn means -
- Moving off the line of attack.
- Moving to gain time/cut time.
- Moving to where your hands and body need to be to do something useful.
3 ways to move -
Turn/twist body or pivot
Shift weight/drop/raise weight
Either individually, or in combination.
Here is a particularly wonderful Judo training clip, and a couple others, showing the beauty of footwork in different contexts. Enjoy.
Here's the random, footwork training drill from Judo with thanks to Erik The Strange for the find
Here's Jay working with a tennis ball hung from the ceiling - fun and tremendously useful solo training if you have the imagination to play.
Here's a nice Capoeira flow ... another partner practice, though in this case the line between footwork and handwork is a bit blurry :-)