Okay, here's how I do it.
1) Draw a straight line
2) Divide that line in half, halfs again, halfs again so you've got 8 segments. The head is one segment and one segment only.
3) The lowest part of the torso goes right in the half way point. Legs are 50% of the height of any given person.
I did that manually a few times, but I feel like I'm getting the hang of it by now. There's some tutorial links buried in here, too, I'll dig them out later.
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