disclaimer-ish...I like writing down things I have sorta "figured out" over the years, and some people seem to find it helpful, but this isn't the word of god and I'm sure a lot of much smarter people have given better over the years, so please understand that this is just my personal experience/opinion speaking and nothing else.
second disclaimer: as I said in the tutorial, this is aimed at strictly cartoony styles, NOT REALISM. I realize there is sometimes a boob-space in real life. My argument is that a cartoony style with lines requires some realism sacrifices in order to draw your attention to more important things, like gesture and shape.
Also I drew the examples in like 10 seconds so.. sorry, they're not the best, haha. PIIIINK
anyway, these are all things I would have liked to know about 5 years ago, so that's why I wrote this. (I'm looking through my old art. YEEP! it's scarier than that ghost I saw the other day.)
Another thing that makes characters look older is the height of their mouth. The lower the mouth is on the face, the older the character looks. I've done that one before.