Here I am copying a frame from the great
Howie Post
that aspiring cartoonists have been trying.
My First Attempt
This didn't work out too good.
I blocked in the background elements first
and didn't leave enough room for the main characters.
My Second Attempt
Better, but I wasn't satisfied with
the way the dust trail was coming out.
My Third Attempt

I erased the trail in Photoshop, printed it out and did the trail again.
My Cleaned-Up Final
It's not as accurate as I'd like -
the main tree's trunk is wider in the original.
I made the main characters taller and longer.
The horse's muzzle should be smaller and point more downward.
The three groupings of tree foliage on the right
need to go down further.
It was pretty hard getting the variety of the circular foliage.
What do you see?