Find your subject and decide on the best media for conveying its characteristics. Would the subject lend itself to a strong tonal handling with heavy shading using a solid graphite pencil or charcoal? Or do you want to make a more delicate visual statement? In this case a mix of soft and harder pencils or a drawing pen might be better. Or try both approaches.
The first is a HB and 6M graphite pencil drawing in my A4 cartridge sketch book. I think I try one with watercolour. It was a disaster. I could not get the graduate change of tones. I found difficulty in handling watercolour on large surface. I then moved on to acrylic. The outcome is slightly better but not entirely satisfactory. Anyway, I like the second drawing better despite failed to manage the graduate tonal changes. I think the composition is better with stronger shadow.