This is a little individual but here a few things that work for me:
For paper filing, if the item or concept is very, very important and it can be filed under more than one title, then I will make a dummy folder that tells me where it actually is.
A surprising number of really important things can be grouped in one heading such as personal papers. "Insurance-auto and home" can probably be generic if you pay it every six months and don't need to retrieve it often. Insurance related to your own business might merit a title like :____(name of business)--insurance, where it would live with other folder related to expenses and operation of the business.
If the material refers to items we own then they are in yellow folder labeled "Lighting and Fans-- we own", while I have plain folder for general information on how to install, select, etc. But if the contents are very limited, like alarm system, then I will still use only the yellow folder because we own it and put any additional information in that folder. If I am interested in something and start collecting clippings and photos etc, I will start it in a manila folder such as "Oriental rugs", but it will be decades before I own one and its provenance in a yellow folder.
One suggestion I have is to make a list of your file headings and map of your system. The more you make a head of time the better because you are less likely to invent new categories. The number of new categories is potentially infinite. If you refer back to your list you will less likely to make a new folder.
As a rule only make new categories if it will: speed locating the file for put incoming info into, speed retrieval, decrease the chance of error. Don't make a new category because it is intellectually appealing, consistent, or because someone else uses it--unless that kind of think is really valuable to you. Do make a new category for a project if you will be borrowing reference material from a folder but not using the entire contents and you will be taking it somewhere out of the office or your home because you could lose it.
The really super simple approach which works for my partner (but not me) is to keep everything important that is permanent (not a project) in one file--no overhead in making folders, no overhead in hunting a folder to put something in it or to see if you are making a redundant category, and when you need an item you just spread everything out and hunt through it.