What Are The Best Practices For Business Folder Structure?

Does anybody have any best practices for how to organise a folder structure?

Don't.

Believe me, you don't want to own the folder hierarchy for any department (except maybe your own). You don't know what their needs are, don't have the knowledge or experience of other departments to make good choices, and don't want to be the company's file janitor.

And if you think they make a mess of it, that's nothing compared to the mess you'll make of things. I know you say you've been tasked with doing this, but the best thing you can do for yourself, is to get untasked from it, quick. This is an example of being set up to fail - no matter how you do it, someone is going to have a problem with it, and complain about or at you because of that.

The best practice is literally "[department head], here's your department share. You're responsible for structure and permission below this level. Set it up however best suits your needs."

There is no "one size fit all", but I would recommend that people be thought to keep things as closed to the physical universe as possible. When I see a person with 10 folder deep hiearchy, then I know they have no clue what files they have and never find anything.

In "real life", you have:

File Cabinets
  --> Drawers
        --> Folders
            --> Documents

Keep it like that in computer files. No more than 3-4 folders nesting.

Depending on the type of files, categories are either by date or by subject. File names would have yyyy-mm-dd-subjectoffile.ext kind of naming.