So a lot of you were requesting about how I draw my heads. So here it is! I'm still new to the tutorial stuff, so I'm sorry if it's not that impressive ;-;

Step 1. Draw a circle. It doesn't have to be perfect. It doesn't have to be neat. Your going to erase it later anyways.
Step 2. Draw two straight lines below the circle- the beginning of the jaw line.
Step 3. Now connect those two lines.

Other steps:
Since usually the head is a little too big for my liking, I shave it down some. You want the top of your persons head to be proportional right? 
Since I did this in a liner, the lines are more wobbly, but with pencil in my case it's a lot smoother.
For a males jaw, do the same steps but for step 3 I recommend doing either a pointer jaw or a more square and chiseled jaw.

Hopefully this helped!