START: READ ME

Start with a clearly defined goal and an overarching narrative you wish to accomplish.

If you simply dive in and start building you will become excited, you will find yourself stuck spinning idea after idea and find yourself unable to finish or burning out. It has happened many times.

If you start with a solid narrative framework and fill in the basic concept, the extra side rooms and concepts you have can be added on as details at a later date - or given enough flexibility and suggestive potential, additions by other players. Little touch-ups as you come back. Instead, determine what sort of impression you want to leave to players and clearly define the limits of such. Is it a sprawling jungle? Is it an organized set of cubicles? Is it an office building, sterile and clean and discomforting? Write it down. Detail the map based on that initial concept. Draw out your map on a grid. Write a single word or a short sentence roughly detailing the concept or narrative for each room.

Then consolidate. You want the map to be FUN. Going through twenty identical rooms is not only a strain on you to write it, but a strain on players to traverse it. If you can compress an excessively long chain of rooms that are nearly identical "This is a long, twisty path" into a singular room and cram the concept of travel into it, do so. Writing directions that only loop back to the same room, or having only two or three rooms that travel in odd directions can do the same work as twenty rooms chained together. You also will spend less future time working on them.

Grant the area enough NPCs and population to give the 'busy level' you want. Cubicles? Tons of wageslaves. Desert? Barely anything. Perhaps a singular weird paracritter or two. Try to squeeze in at least a related job linking into that area from somewhere else.

Congratulations. You now have a basic zone ready to go and be released. You can go back and finish it later. Maybe listen to players' suggestions on what to add.

TL;DR LIMIT YOURSELF SO YOU DON'T DIE

Oh yeah, and set the name for everything to be different, so you don't end up with an identical stack of rooms and NPCs that you have no idea which is doing what.

And clone is your friend.