Room and floor numbering conventions for large to midsized dungeons: most popular, advantages and disadvantages? [closed]

Question

Introduction

I have been creating some multi-floor dungeons. It took awhile, but with time I found software, a notation format, and fidelity level that suited my needs. The one thing I'm still not satisfied with is my method for numbering dungeon rooms. I have tried to use third party material as a guide, but all of the published adventure modules that I own use relatively small dungeons, and therefor a room numbering system that is too simple for my needs.

Context

My dungeons typically have the following properties:

1. 5 or more stories tall.
2. Floors below ground level, i.e. basements, cellars, lower levels.
3. Multiple points of entry.

Currently, the rooms on the ground floor are "A1","A2", etc., and then the second floor "B1", "B2", etc. Basement rooms are "LL1", "LL2", etc.

What trips me up:

1. How to number lower basement floors
2. The order that floors should be listed in GM notes. Do I start with the ground floor, from the lowest floor up, or from the most probable point of entry?
3. How to deal with double-high rooms that intersect with two different floors.

These dungeons are mostly for my own use, with my own group. That said, I usually have to prep far, far in advance for our games, so it is very important to organize my notes in the most intuitive way possible, as if a complete stranger will be using them. In the past, I have left out critical information because of bad note organization and formatting. Making things look professional is helpful and important to me. I do have some interest in sharing this material with a broader audience one day.

Question

Of course I am not looking for the best room numbering system — that wouldn't be SE appropriate. Instead, I am soliciting examples of different RPG room numbering systems that have become the most popular over the years. A top 3 list of the most commonly used systems, for example. In addition, please provide an explanation of how these different systems meet or do not meet the aforementioned criteria?