Have you ever seen sketches either from an artist's sketchbook or in a gallery and there drawings always look really sketchy, there's something about them that you really like and want to emulate. Sketching isn't about drawing a likeness in a portrait or drawing things accurately, sketching is about being loose and bold and not worrying about making mistakes, letting your real feelings come out.
The whole point of sketching can be done in two different ways, one way is sketching as a preliminary to a painting or a finished drawing, the other way is just for the art and fun of sketching which if done properly can really turn into a work of art by itself. The sketch on the left is full of life and energy and you can only achieve this dynamic and rhythmic flow through sketching whether it is with watercolour, oil, charcoal, acrylic or any other medium.
In this detail of the same sketch we can see all the scribbles and marks that I have put down and each mark or scribble means something whether it is the form of the hair or the way tone has been laid in. The detail looks abstract in this example till we see the full sketch and then realise that everything is there that needs to be, look at the full size sketch and you can see what these marks and scribbles describe.To do this sort of sketching you need to relax and let yourself go and not to be afraid of making mistakes and to have an understanding of form and shape. Once you know about form and shape try letting yourself go and lose all your inhibitions and preconceptions of what you might think drawing is all about. The example on the left is a simple sketch that is fluent and rhythmic, I wasn't really bothered about toenails or whether there was an highlight in the dogs eye. This sketch took two minutes to do and it is a good idea to set yourself a time limit to see what you can achieve.