Lesson I learned from creating the module "The Overrun Mines". I labelled the map, but within the original version of the text, I mis labelled the module / room numbers, and wound up with 2 - "Room 13's". Here is how I plan to combat this issue in the future.
1. Draw all maps
2. Label all maps in GIMP "Map A", "Map B"
3. In word processor , prior to doing any writing whatsoever create pages with Map A, and then add in all the room numbers (while looking at printed map). So you will have the following
This way you don't miss any rooms! or label something wrong and it becomes confusing as hell for the guy trying to run your module.
4. Write out all descriptions to your hearts content
5. Upload to drivethrurpg.com
6. Steal underpants
(that'd be a South park joke, stop at 5).