Here is an interesting exercise by Mario Foglia .

He wrote:

Hi all,
after attending the First Italian Sketchnote Workshop, I usually go to lunch with some sheets of copy paper, a good pen and enjoy my time doodling. This was inspired by the work done by Mauro to recap his "3 days with Mike Rohde" in Prague: Catch the Dominant Lines of an Object, and remember "Sketchnotes are Ideas, not Art".
Ciao

For those who wonder what "3 days with Mike Rohde" is