Expressions in After Effects is the underlying language that can help you automate and extend some of Ae’s functionality. Evaluated on a per-frame basis, it’s not something to overuse. There are some definitive expressions that will make your work-life much easier. Even the most novice of users are familiar with one of them, Ae’s wiggle expression. It lets you automatically and randomly move elements on the screen with some simple syntax. If you are looking for a list of useful expressions, then you should definitely check out Sergei Prokhnevskiy’s guide to 16 Useful Expression in After Effects. That was posted a long 8 months ago.
If you feel like you need to add to your After Effects expression knowledge, there is a bit of good news. Sergei has posted a look into 19 more that you should consider knowing and using.
Quite a few Ae users will shy away from the expression language, simply because they look too complicated. Sergei hopes to alleviate that fear: “I want to change that by showing you simple expressions you can use daily. They are easy to remember and quick to execute. Give this tutorial a try and you’ll be amazed by the simplicity of these expressions.” Both those tip-packed tutorials can be seen here.