I've gotten this question a few times, so I guess I'll address it in a journal- how to learn to animate (ponies?) in Flash!
First off, I'd recommend reading any of the "How to Cheat in Adobe Flash" series of books by Chris Georgenes- they're really awesome primers on how all the various bits and animation features in Flash work.
Here's the CS5 version
As for animation approach, besides the info you'll get from there, Keith Lango's tutorials are surprisingly relevant for Flash symbol-based animation, despite being written for 3D:
Pose to Pose Keyframing and How It Works (2001)
Overlapping Motion: Breakdowns Can Be Such A Drag (2006)
For general animation know-how, of course you should check out