I love the basics of just pencil on paper. Usually, I just use a #2B, on my Canson hardback sketchbook, and I can flesh out an entire drawing that way. It's interesting to see how the character of the drawing changes once I begin painting it. Sometimes I like the outcome of the painting in which it looks different from the original sketch.
On the finished frog piece I kind of missed the warty-ness of the original sketch, but all in all I liked how the personality of our little frog here turned out.