How to get started?

I personally just dove right in whatever search interested me. BUT, I do think helping people with unidentified media is a good start. It kinda gets you to think critically in how to search for stuff, because the real challenge is not totally knowing what you're looking for.

Here are other tips:
1. Archive.org is a good place to look because it's literally archive.
2. Wayback machine is part of archive.org and is a great way to scour old web pages for clues.
3. Google has a search option that can pinpoint what you're searching for through certain years/decades.
4. Sometimes reddit will have similar posts to the ones on here (tip of my tongue, lost media), and more clues can be gathered there.
5. Contacting involved people is a big part of searching, but don't go willy-nilly on it. Suggest it first and see what others think, and if you do contact someone, DO NOT HARASS THEM. Sometimes it will take a month or more for a followup. And sometimes these people have already been contacted.

Have fun!