I've been messing around in After Effects for a while now, in fact I had dedicated the last 24 hours to that cause, and I must say it's been very fruitful.
For starters, I've gotten some grasp of expressions, specifically "loopOut". I've also been messing around with the Wiggler and some plugins.
I've said this multiple times, and in my Photoshop Basics tutorial you'll definitely hear it a lot:
EXPERIMENTATION IS EVERYTHING!
That's perhaps the one thing that makes self-teaching more flexible and if you're not to experiment you'll never learn anything (other than the stuff that people teach you in tutorials).
What I like to do is take stuff that people mention in tutorials and stop halfway and mess around with the values given. For example, I learned about the "wiggle" expression from a tutorial I read somewhere, and as I completed the tut I created a new project, drew an ellipse and got to work with messing around with Positions and Scale and Rotation with wiggle. What happens if I typed "wiggle(10,10)" or "wiggle(.24,100)".
That's just the start. You can go wider by going against that stubborn instinct and actually go into the After Effects Help (F1)! I went in and typed in "wiggle" and read what I could about it. In the process, I found the "Expression Reference" pages and learned about loopOut and adding Math figures and also linking two controls together.
It's funny how everyone rejects the Help system that Adobe so painstakingly worked on. Sure, it can be VERY vague at times, but I will say that it helped me learn a lot in Photoshop: Vanishing Points was a good example, though it never explained exactly how to use it, it did give me an idea of what it did so I could decide if it was something I'd want to use or not, and it turned out to be a very handy tool.
So, ladies and gentlemen, as we continue to learn about these programs, I'd like to point out just one more time:
Experimentation is Everything!!