This was a question my grandfather asked a much younger me one day when I excitedly showed off my newly learnt kicks.
I think we all agree by now that we would be surprised if our opponents did in fact stand still.
If you are already an accomplished fighter you most likely know the things I am about to tell and you are then welcome to skip this post. If you are someone who has trouble landing blows you may find this helpful-
The secret to making your throw, punch, strike, armbar or wrist lock hit its mark lies in timing.
Kihon (basics) and kata practice do not teach timing and may have you imagining an opponent just waiting for your attack to reach him. Timing is developed with sparring practice.
That- most of us seem to know. What few seem to know, however, is that meditation is actually crucial.
Thoughts and emotion actually slow down your responses. Guessing is also thought- and it does not help. When you have pushed all that aside what you have left is...
Now- What should you be aware of?
Fact is- I don't have enough time for a complete list of things to notice. A grappler would like to see the arm about to straighten. A striker would appreciate that rib opening up as the opponent punches. You may appreciate the opponent about to be in range for your favourite kick...
And when you stumble upon the opportunity which you appreciate, but not consciously look for, your body should seize it without hesitation and without thought. :)
Then, I hope, you realise why a martial art can be regarded as moving Zen.
Wenhsiuquan focusses on this type of awareness.
I can type long passages about transcending the ego and reaching a higher plane of awareness, but your best hope of understanding it is training in the way I have just described.
Enjoy your training. :)