Before I painted I used to work mainly with the pen & ink medium. I was fond of the stippling technique and most of my drawings were large pieces...up to 18"x24". That's kind of an insane size to work with considering the small pen nib sizes I used. Stippling is the process of applying single dots of ink one at a time with a Koh In Noor Rapidograph pen. The ink work is usually done over lightly drawn pencil lines used as the guide for the artist to follow. I enjoyed pen & ink work. It's hard on my eyes now but I've loggged thousands of hours dotting away quite happily.
The effect of stippling is much like printed images you see in the newspaper....halftone images, a reprographic printing process, is simply an image being formed by dots of ink creating toned images which I call value images. If you want to better the values in your painting do pen & ink work...you'll see values easily after that.
When I started with pen & ink there were not a lot of art instruction books out there for it. Wanting better compositions I turned to reading painting books. Composition is composition so it worked for me. As for colors you just insert values. One thing about your point of interest is putting it in the right place and then directing the eye there. I had a drawing of a boat that really illustrated this point well.
Here is the initial point of beginning the drawing. Tha man working on the boat was my point of interest. That area should have the darkest darks and lightest lights.
My favorite pen....Koh In Noor's Rapidograph which comes in different pen sizes and are refillable.