They let the students choose the type of music to listen to throughout class….and their CD case is filled with reggae and classic rock.
You have to keep your name tag on your desk, five weeks into the semester because the professor claims to be "bad with names".
Long Hair….'nuff said
They say cliché things with a smile on their face like "I've been to college too" to try and hint towards their rebellious pasts.
It's an art teacher.
They are late to class and take extremely long to grade/return assignments.
When you wear a tie-dyed shirt to class, the nod their head and wink at you while saying "I get it."
He or she is constantly snacking on food.
They give long, rambling, go nowhere speeches that fail to make any kind of point.
When they see you do it…..you don't get in any trouble.

If any of your professors meet one or more of these criteria…..there's a good chance they've toked on some bud at some point in their life.