Value seeing and sketching requires lots of practice. Pencil shading will give your line drawings values. I try to add pencil shading in just 3 values; light, medium and very dark. I let the white of the paper be the white or lightest value I see.
I started out my sketch this morning with a corner of our family room. I tried to sketch what I saw directly in front of me.
I suppose if you wanted to you could produce more definitive value sketches using a light pencil like an HB and a darker pencil like a 4 or 6B, I didn't use 2 pencils for my sketch. I grabbed the nearest pencil a 2HB. I find if I get too fancy with my supplies I don't do much drawing.