Nostrils! Who ever talks about nostrils?! If you get the angle of a nostril wrong it will completely screw up a face and even if you have no idea how to hold a pencil, you’ll see a nostril at the wrong angle and it will subconsciously drive you mad.

Reason No. 1 You Should Be Sketching Every Day – Flying Meat Blog http://shapeof.com/archives/2013/3/reason_no._1_you_should_be_sketching_every_day.html