There are a couple of ways.
The most recommendable way is probably doing specific value studies, like landscapes.
You already found the asaro head, thats a big boost on the way to seeing planes and specify them with values.
Squint your eyes often
and make a habit to do so often.
Colors will get filtered out and you are left seeing only values, try to compare the values you are seeing (What makes it stick out? Is it brighter or darker than the surroundings? Where is the light source? Is there bounced light? What kinda shapes does the shadows / light have?)
Keeping it simple and readable is a hard thing to do at first, that's where shapes and the planes come into play, don't stress over it, you get the hang of it when the other things get a bit easier and start to connect one by one.
Oh and if you are drawing on other mediums too, that can be really good.
In graphite or charcoal you only have values to work with and you need to be extra carefull of any shading and marks you do.
As time goes on you will get better at it, it's one of the most important things to learn, you definitely cannot skip this stage so take your time ^^
I'm gonna give you a couple of videos you can check out when you have time, they are all covering the exact thing you need to look out for.
