To get started creating animations for Lottie in After Effects you'll need a few things
Get the latest After Effects from Creative Cloud here.
Download and install the latest version of the Bodymovin Extension for After Effects. Detailed instructions here.
After you're all setup with those three things, check out our general tips. Since not all After Effects features are supported see our supported features list. Lastly check out some workflow overviews in our SVG/Sketch to Lottie walkthrough or our Illustrator to Lottie walkthrough
All of these goodies are Highly recommended. They arent essential, because you can still create for Lottie without them. But your workflow will be significantly faster and better with these extra tools.
Overlord by Adam Plouff is the ideal Illustrator to After Effects workflow. It is an extension for After Effects and Illustrator that helps get artwork back and forth between the two programss. "Think of Overlord as a way to use Adobe Illustrator as a drawing plugin for After Effects." -Lester Banks.
Parametric converter made by Kyle Martinez converts bezier shapes to parametric shapes. Its super helpful when you have an illustrator file that has elipses or rectangles as paths, and you need them converted to the parametric shapes with size controls etc.