Quote from SoulEater

K, heres some help. The stick figure barely moved at al, and the animation was choppy when you moved more then one figure at once. There wasn't any easing which ruined a lot of the animation and also the reactions and physics were off.
For easing: Easing is used to make things look more natural. Like this diagram shown here. |-|--|----|----------|--------|------|---|--|-|

Stiffness: Stiffness is when a stick doesn't move enough, or a stick's limb doesn't move according to a movement. For example, when you jump in real life, your arms kind of bend on the way up and float upwards on the way down. In walking, the head bobs slightly due to gravity and force when a foot hits the ground. Something to help a little would be to move every limp on a sticks body every frame, even if it's one pixel at a time.

Choppyness: Choppyness is caused usually when you move more then one figure at a time. You could forget to move the next limb/stick during a frame, making it stop and twitch for a while. A way to help that is to not forget about the other figure!

Smoothing: This is similar to easing, except it is used to make movements more graceful. To help add onto this, always leave a part of a stickman in it's onion skin.

Physics: Physics are things such as realism. For example, if a stick figure bends over, he has to get back straight some how, make his leg go back as to make the weight of his leg pull his body back upright.

I hope this helped you, I spent like 10 minutes on this post!