Where do you put your ideas?

I am currently looking for a system which will help me execute some of my massive backlog of ideas. By “ideas” I include my hundreds and hundreds of story outlines for films with a handful of finished screenplays, but also things like: alternative income streams, or day jobs, or skills or abilities I’d like to learn/​get (coding, traditional animation, dance the Tango, conversational Italian), as well as a host of other projects.

Before I get to the determining how to better pick which ideas I should pursue (Update: see my investigation of my idea choosing decision making model here), I was wondering if there was any more I could do to optimize my current idea recording method. Some of this overlaps with the GTD concept of the “Someday” bucket. But what I don’t like about that is that I’d very much like to ensure I review and act upon some of these ideas.

So how do most of you record your ideas? Where do you put them? Where do you keep them, not so in the dark as to never seen sunlight again?

I’m from a film background, so my knowledge of idea-capture is influenced by anecdotes of everyone from Vladimir Nabokov’s index cards which in the early gestational stage he describes as ”...including the accumulation of seemingly haphazard notes, the secret arrowheads of research”, Joan Rivers or Bob Hope’s archives of decade’s of accumulated jokes organized by subject, or the unfiltered and uncensored NO-NO sessions of Robert Clampett at the birth of a cartoon. To Jerry Lewis typing out between shows the screenplay the Bell-Boy, which to be fair is more of a anthology of isolated jokes than a continuous narrative?

But what about when you have an idea for an app? For research? For an algorithm? Or yes, career moves and similar choices? Where do you put that idea? How do you ensure you don’t lose it so that you can maximize the chances of doing something with it?