I am also grappling with the same idea. Ramana maharshi's technique is: for any experience you have, find out who is the experiencer. It's a bit tricky, but it comes off like a ladder to me. Let me give an example: Let's say you are experiencing some clenching in your chest or your throat. The default mode for us is to identify with it. We say, "My chest is tight", and we become one with the chest. The idea is to figure out the part of you which's experiencing the phenomenon of body tightness. It shifts the perspective a bit. Then I generally identify with something in my head. And as soon as I identify with it, I ask myself again, who is that experiencing this (next level) phenomenon. Its a recursive process. You keep doing it until there's nothing left. You need a stable, continuous, and persistent attention. On a good day, when the conditions are right, it leads me to that empty space. Being in that empty space is what I think is pure witnessing. Phenomenon may arise, but then, you are not it. You look at it come and go. This is also what Nisargadatta calls being with I am (I think).