Published by Adobe, these two guides should be your starting point when you finally dive into scripting for After Effects. It will give you an overview of scripting in AE and acts as a great reference.
4) ExtendScript Toolkit Tutorial Series
Are you more visually oriented? Me too. Check out this tutorial series posted over at Pro Video Coalition. There are currently 8 episodes that cover a range of topics to give you a good overview of scripting and the tools at your disposal.
Dan Ebberts wrote the book on the geometry/math behind SO many expression-based animations. He gives line-by-line breakdowns of each expression so you can understand how each part works to produce the final animation/behavior. If you want to understand expressions/scripting in AE, Dan Ebberts is quintessential.
6) AE Scripts
Finally, one of the best ways to learn more about scripting is to read code written by other people who are good at scripting. AEScripts is a HUGE repository of scripts showcasing almost every possible use for scripting. And what’s better…many of the scripts use a “Name Your Own Price” system so you can support the programmers without having to break the bank.
Scripting can seem daunting when you don’t know much about it. But as you get deeper into it, you realize that scripting is, in many ways, the same as learning After Effects: intimidating at first but the more you learn, the more you can do.
Check back soon for my continuing series focusing on all the tools you need to script in AE.