1. Sitting and the right hand position

If you’re not completely new to the guitar, I assume you already know how to sit and hold this instrument.
But anyway, here are a few words about it.

When speaking of playing fingerstyle, one of the most important things here is the ability to hold a guitar
stable when you use hitting and kicking percussion techniques.

I’ll show you the way I hold a guitar. 

I always use a foot rest (footstool) when playing in a sitting position. It helps to hold a guitar a bit higher

so I can lock the guitar between my chest and my leg. Also, holding the guitar this way helps to avoid

left hand tension and backpain.

You can use any steady object as a foot rest.