Nice critiques J, if you have time feel free to crit my comic too
Practice drawing your own face in various expressions in a mirror. Get good at it. You will find that all those shorthand tricks cartoonists use to draw simple faces are directly tied to things your face actually does- like eyes squinting up in a certain way when you smile. Humans are built to recognize these symbols on sight. The better you know how they work behind the scenes, the better you can trigger that recognition by drawing a few simple lines on a circle.
I suggest making a reference sheet for expressions, I drew one for Maskerman a while ago and I must say that it's a great help to easily find the right expression when stuck.
Please excuse the bad scan, it's not inked _________________