One of my favorite things I learned in school was Prof. Vakil's "Three Things" exercise for getting things out of talks: The theory is as follows. If you can get even three small things out of a talk, it is a successful talk. And if you can't get even three small things out of a talk, it was not a successful experience.
(In this page, "talk" is interchanged rather generously with "stuff I liked or found memorable".)