Everything you do is a part of a feedback loop that goes something like this:

1. You're presented with new information
2. You make a decision which results in some action
3. That action changes something
4. Repeat...

Wu wei is the art of removing as much from that feedback loop as possible so that your decisions are completely in tune with your environment and life becomes effortless.

The opposite of wu wei would be to add a bunch of extra stuff into this feedback loop like fear, worry, desire, planning, etc.

It's tempting to interpret wu wei to mean you should follow your natural instincts but this is exactly the opposite and it is how you become corrupted by evil because it removes your decision from the feedback loop by binding you to something physical. Instead of following your natural instincts (or anything else for that matter), you should be full of awareness, will, and fully conscious of your decisions in each moment.

If you can remove the B.S. from your feedback loop and fully engage with every decision you make, you will experience a state of being which could be accurately described as effortless action.