Try and remember that heads aren't pure circles or ovals. It's not one definite shape, but more of two Two circles overlapping. The top circle is always bigger.
Tutorial
This is my ever-growing tutorial for anyone to use. I permit you to save and open the files in paint, to get a good, up-close reference but you may not edit them or copy and paste them into anything. They are not bases of any kind! I hope they help.
+Proportions+
Shape;Distance
Try and remember that heads aren't pure circles or ovals. It's not one definite shape, but more of two Two circles overlapping. The top circle is always bigger.
The eye normally starts about a finger's width (in porportion to the drawing)from where the brow starts and ends at about the same place.
The lips are about twice as far from the tip of the chin than they are to the botton of the nose and the corners of the mouth should be close to a finger's width from the sides of the nose.
Don't forget Adam's poor apple! In reality, this drawing's neck is far too thin. But for a cartoony style, it's acceptable.
Just remember that tits aren't balls unless you get em' done that way. Natural breasts are a bit more like water balloons than anything else.