The two sketches above were done in watercolor, feeling out ideas for larger paintings, and they were done very quickly; my objective was to see if I liked the overall look. I don't believe either one was carried on as a painting.
Sometimes I just like to work on drawing, especially portraits. I am still working on my goal of doing 10,000 faces in order to get better. When I do something like the above (if my recollection is right, it might be a study from a painting by Ilia Repin) I am working on learning to quickly get proportion right, building confidence in translating without distortion.
These two were done with markers, and the goal was to evaluate composition and value. I did later work these into paintings, and the work done in the sketches helped make the final result stronger. This particular sketchbook is 98 pound paper, meant for mixed media, and still the markers bleed through, so it's important to sketch on only one side of the page. In my opinion, it's helpful to have a variety of sketchbooks, some better for pencil, others better for charcoal, still others for watercolor. The problem I have is trying to use them all often enough. It's one thing to pull one out for some preparatory work when building toward a painting, but I wish I could do better in sketching in the field, just for the practice in seeing and drawing. In fact, that's where I'm headed right now, out to find some subjects for study.
Happy sketching to you all!