My Documents
I recommend against having more than two file folders deep. Level 1 is the main divisions (Inbox, etc.), within which you have subfolders (i.e. Level 2). Within the subfolders you have only files... not more folders. This makes for more efficient/effective retrieval.
Put an "_" at the beginning of the folder name for your main categories (Inbox, Project Support, etc.) so they stay at the top for quick reference. Then, staying in the main My Documents folders, create folders for the rest of your data. Name them based on whatever name first pops in your head. If you will need subfolders for that topic, then capitalize the folder name. Fill the topic folders with files -or- subfolders (not both), then fill any subfolders with only files (not more subfolders). So, you have a maximum of two levels of folders, and folders contain either only folders or only files.
My Documents could be set up like this:
_Inbox
_Lists and Checklists
_Project Support i.e. Project-specific
_Read & Review
(the following are sample topic folders)
aardvarks
bananas
chiropractic schools
Major Topic 1 (with A-Z subfolders)
Major Topic 2 (with A-Z subfolders)
maps
menus
...
zoology
Other filing schemes require more maintenance than the above A-Z. an A-Z sort by topic also facilitates skimming. Name the folder by the first name that occurs to you, as that will likely be the first one that occurs to you when looking for it.
Note that with only one screen full of well-chosen file folders (~50 of them), and a single level of subfolders (~50 per), you already have up to 2500 file folders... each of which can contain up to one screen full of file names (~50 per folder), and you have space for over 100,000 files without having to ever scroll down through screens of files or click more than 2 folders deep. All those clicks add up.
Choose filenames that tell you what you'll want to know when you go looking for it. "2008 household budget" beats 7R3WWgfje.PDF any day.