Some things I found helpful were using squares, circles, triangles, and also a sphere with two curves showing direction object facing.
In life drawing I found it extremely helpful to draw in boxes or circles or straight lines to warm up for drawing.
I also found it helpful to draw distorted circles that looked like they were squashed. Afterwards filling in arms and legs and head.
Check out Eric Goldberg's amazing animation discussions on faces in Character Animation Crash Course.
Regards,
Nate
