Leverage is usually the means of exchanging direct force for control.
Let's consider the clockwork of a mechanical watch as an example. The gear work of the watch (the leverage system) refines the force gained by the winding up mechanism, and punctuously parcels it out to be able to move the hands of the clock.
How to leverage? Observe the system. Understand the system. Find the strengths and the weaknesses. Find the key points. Understand the dependencies.
When you understand the system, apply the minimum necessary force at the key points to make the system work the way you want it to.
If there is no system, build one! If you have a big goal, break it down to small steps, and if you can, use a leverage system to move forward ten steps for you when you make one.
Using brainpower to leverage force is the advantage humans have. If you learn the general idea of how to leverage, you can apply it to all kinds of aspect of life.