"How to Draw Spirit" by animator James Baxter:
https://www.youtube.com/watch?v=n8hncmoniFoI found this tutorial on YouTube on how to draw DreamWorks' hand-drawn animated feature "Spirit: Stallion of the Cimarron". It's pretty in-depth. It begins with the "skeleton" - some basic structure lines and joints - and then the "muscle" is drawn around it. (The horses in the movie are beautifully animated). Here's the sketch I came out with:
(The video also includes instructions on coloring the sketch, but I didn't do that step.)
I also did one with Maximus from Disney's "Tangled" by animator Marc Smith. This one a quicker instruction on how to do a cartoony bust of the character: