@Xeon, Hey, Hope ya remember me,
Anyways, an extremely easy way to be extremely good at proportions is to do the follow:
When drawing any head, draw either an oval-like head-shape or a box-like one, or Loomis' Ball and Plane Method; I prefer the box, it shows you clear perspective and the ball and plane method can fit within; Anyways, draw a line from the nose's edge, the line should align at the down edge of the ear, block-in the ear, from it's top will be the eyes, at that point you've blocked in all of the basics, use Loomis' Ball-And-Plane Method afterwards, inside the box, What about the rest of the proportions? Here's the catch: Head over to "The Drawing Script" link I've posted before and tick only heads, and draw 3-minute gestures, in a short-while, you would absorb proportions easily, park and cafe sketching is as effective if not more.
"Without Music, Life would be a Mistake"-- Friedrich Nietzsche (Although I never actually listened to any music by Friedrich Nietzsche, I like the quote]
"Time is a vindictive bandit to steal the beauty of our former selves. We are left with sagging, rippled flesh and burning gums with empty sockets."--Raphael (Now that's my favorite quote, from my favorite artist)