There’s a new book which I would highly recommend: Animating with Blender, by D. Roland Hess (ISBN 978-0-240-81079-9).
This book takes you through every step of creating a 3-1/2 minute pure-animation short subject with Blender. Yes, every step. Yes, with Blender.
No, this should not be the first book that you read about Blender. You need to learn about the product first, to stumble-and-fall with it using some other books. And do be sure that you are using the most-recent (i.e. yesterday’s … no kidding …) version of Blender.
This book will show you, “this is how it’s done.”
One thing that you need to bear in mind is that, even for this dude (“Harkyman” right here at CGTalk), who has been doing this for 20 years and who wrote substantial portions of Blender, this film was a project that spanned multiple months of hard work… not including render-time.
I do believe that “making a short subject” of any length is vital experience, because it obliges you to “wear all of those hats” and perhaps thereby to find out which one fits you best. But your first project, and maybe your first several, should be short and focused. Make a series of one-minute pieces about “the Pyramid people.” First, they’re just moving around. Maybe later you put lips on 'em and try your hand at syncing. Maybe in the third film they bump into an unexpectedly-realistic model of something. Four or five pieces down the road, one of the Pyramid People is wearing a really cool GLSL-based texture. The thing is, instead of “biting off more than you can chew” and choking on it, try to learn about specific in “really small bites,” bringing each little piece to completion so that you don’t lose your momentum.
Every one of them is an exercise. None of the exercises are “complete,” in the sense that they exercise “everything,” but every one of them is completed. And, you know, you really can tell a compelling story about, and with, pyramids.