When I started jotting down ideas for stories many years ago I didn't have a lot of foresight in the way of organization. Even today those ideas are stored in a batch of electronic documents with seemingly unrelated titles, lumped together only in a 'stories' directory. Some I can remember just by glancing at the name of the document, but most I need to open up and scan through to remember what they were about. Some have nothing more than a half-page of notes, others have 10,000 or more words and the start of a real structure.
Since I started publishing I've become much better about organization. The Bladesmen Lords series has plenty of artifacts related to it now, from promo posters to original pictures of the cover art to the stories themselves in various formats and drafts. Partway through writing City of the Lords I organized all of this better instead of throwing it all in a single directory and trying to remember what belonged to what. The third book - which is progressing well, by the way - is set up alongside the other two but separate so I can keep its assets properly catalogued.
I've lost a lot of hard drives over the years, and I sorely miss a batch of story ideas that disappeared over a decade ago. They're gone now, but I remember enough bits and fragments that I wish I'd properly backed them up. I know better now, and keep copies of all my latest works spread through several areas both within and without the house. That doesn't help the organization - it's easy for things to get out of sync - but it keeps ideas from getting lost.
Start organizing early! Someday I need to spend a few days and go through all of those old ideas to retitle them, group them where appropriate, and make sure I can get to them easily. Don't wait as long as I did.