Even though not comedy per se, I do weekly satire.
It might sounds cliche, but I get idea from my daily life.
I focus on contrasts and contradictions around me to frame potential ideas. Once the idea is identified, I generally refine the message into a two liner max. I just list these on a note book (actually random pieces of paper stapled together...). I have a lot of ideas, good and bad... My brain unconsciously process and sort these ideas, and some will naturally stand out after a while.
Once I select an idea worth investigating, Iāll brainstorm related concepts (situational, emotional and visual) and create links. That might take some time, but eventually an episode will form, and Iāll start actually drafting...
Example
For last episode of Effy, I was doing a lot of stern graphs for my daily work. The kind of graphs in which the slope inclination means butter or no butter for many people, so no time to linger on emotions too much. That felt abnormal so two liner (in that case three words) -> daunting emotionless graphs (daunting and emotionless being the contradiction)
I link that with: fluctuation / curves / mood / rational / 21jumpstreet experience (because I crashed one night with irrational mood which I guess was compensation, and the show was on) / losing oneself / without self / EMH / rational markets...
Then I pictured in my head a graph showing someone crashed on a sofa, contrasting abstract graphs with real emotions... and that came out:
And I built the episode around leading to that...