Take an organic subject matter, some small shells work well but leaves, flint or bark are great too.
Put on some of your favourite music.
Mark make with charcoal to the beats, rhythm and flow of the music.
Work on the biggest paper you can find or tape some together. Remember your rubber is a tool not just a corrector, you can make marks with it in the same way, especially with a putty rubber or Blu Tack by warming it up and moulding it into shapes and points.
Use the tip of the charcoal to draw but also hold it on its side, breaking it to whatever length suits you. You can make extremely sharp straight lines by using the side to go in the direction of the length of charcoal as well as making big sweeps of tone by going from side to side.
Slightly textured paper works better with charcoal, but normal sketchbook paper or cartridge paper will do.
Materials: Charcoal, rubber, putty rubber/Blu tack. Fixative/hairspray.