here is another sample of a lesson from the mysterious secret cartoon college:
I suggest (if you don't already) supplementing your cartoon studies with some life drawing. (I know this is a photo, not a live model)Why should you?
Because when studying Preston Blair type construction - made of spheres and pear shapes, there is a tendency for some cartoonists to think cartoon characters are made up of balls piled on top of each other. Or they draw the balls and pears too mechanical and not organic enough.
Also another point: THE STIFF PERIOD OF LEARNING
Any time you learn a new concept or drawing skill, when you actually first try to draw it you will probably be very stiff, because you haven't practiced the concept enough for it to sink in. This is the tough period of learning anything.
Drawing 1 - STIFF, study drawing. Slow and careful, grinding my teeth
When I first drew this guy, I slowly, carefully blocked in the construction first - having to think about the types of shapes that make up a strong man. I couldn't use balls and pears because real life is made up of more complex parts. They are still solid forms, but bendable solid forms. They are complex organic forms.
Once I finished the first drawing, I knew a lot of things I didn't know before: How the traps are shaped on one side compared to the other in a 3/4 pose. What biceps look like from 2 different angles in relaxed mode. How the biceps fit next to the triceps and the space between.
How muscles weave in and out of each other under the skin. The feeling of flesh, not just the wooden proportions of man.
How the 6 pack works as a whole unit before it's split into parts
How big pecs hang in repose (it's very important to know this, especially for you girls)
etc.
Drawing 2 - Looser yet still solid, more organic and confident, more fun to do
my conservative attempt at Chloe's style
Then I redrew the drawing faster and looser - while still trying to keep all the forms solid, but to make them less stiff, more flowing: more ORGANIC
my conservative attempt at Chloe's styleSome artists go too far in the direction of organic lines and get wobbly formless characters. I actually really like this one below. It's very funny.
Some artists are too stiff and draw mechanical characters.
Ever see those Gene Deitch Tom and Jerrys made in the 60s in eastern europe? They are a total misunderstanding of the 40s American animation style. The characters are drawn stiff and move stiffly. They look like they are made of badly drawn balls stacked on top of each other. 
Here's a weird combination of wobbly and stiff at the same time. That's an achievement! Whenever anyone draws Tom and Jerry now, they give them these bulbous balls for toes that they never had in the original cartoons.The trick to good drawing is to combine solidity with fluidity. And life.
You have to look at both sides of an object (say a bicep) and draw the whole form, not two lines on either side. Look at the form inside the lines.
I made a mistake in my muscleman drawing above that I warn everyone else about: the side of the man's head that is closer to us (on the right) is too cramped. I squashed the space between his face and cranium. Lots of us have that problem.
Preston Blair Forms don't work for everything!
I saw one student's attempt at caricatures and he was trying to construct them as if they were Preston Blair forms.
That doesn't work.
When you draw from life- DRAW WHAT YOU SEE
Don't try to impose what you think things are supposed to look like. We aren't made of balls and pears. Only old animated cartoon characters are because those kinds of forms are easier to tun in space and they provide a simple foundation for many other concepts and principles.
What you learn from drawing from life and using your eyes to observe new things can then be applied to your cartoon drawings in simplified form.
Very Organic and Solid Preston Blair Forms
These drawings are not remotely realistic. They have no real anatomy. They are entirely made up of animated cartoon forms - spheres and pears. Yet they don't look mechanical and they are full of life. They aren't balls piled on top of each other.
Here it is done wrong: 1980 Tom and Jerry at Filmation, Balls on balls. A complete misunderstanding of the 40s style. We used to laugh and cry at these model sheets at the same time when working on these cartoons. (Thanks to Tom Minton for saving these hilarious monstrosities)
These Eisenberg characters are much more convincing as life forms, even though they have no literal realistic anatomy.
These drawings are not remotely realistic. They have no real anatomy. They are entirely made up of animated cartoon forms - spheres and pears. Yet they don't look mechanical and they are full of life. They aren't balls piled on top of each other.
Here it is done wrong: 1980 Tom and Jerry at Filmation, Balls on balls. A complete misunderstanding of the 40s style. We used to laugh and cry at these model sheets at the same time when working on these cartoons. (Thanks to Tom Minton for saving these hilarious monstrosities)
These Eisenberg characters are much more convincing as life forms, even though they have no literal realistic anatomy.
That's because they obey some principles of reality. They are organic and solid at the same time. Asymmetrical in a natural way. They have weight. They are not robotic.
You can really feel this drawing of Tom smashing into the log. It makes sense. It isn't random distortion. (His belly is accidentally painted wrong; that's why he looks skinny at first.)It's organic and solid at the same time - and obeys some expected sense of physics.
Don't draw stiff (except when learning and you can't help it). Don't draw wobbly. Aim at drawing convincing solid organic life.
SOLID, YET PLIABLE OR "ORGANIC"