To come up with ideas, I either listen to chill/lo-fi music (music that doesn't require concentration (ex: songs with meaningful lyrics), nor is too loud) or I don't listen to anything and I drink tea while spacing out/staring at the ceiling.
But sometimes, ideas come spontaneously, that's why I always have my mp3 with me, so that I can write them down (even if they look crazy or stupid, I just write everything down since I don't know what can be useful or not).
Basically, I list all of my ideas/all of the topics I'm interested in or want to talk about, then, I sort them out by theme.
And then, I choose one or more themes (as long as they go with each other) and I start writing my script/storyboard.