When you write, how much detail should you include and how much should you leave out. For inspiration, you may want to think of what makes a map useful.

One of the most famous examples cited for design and ease of use is the map of the London Underground. If you know the station you need to get to and you know where you are then the map makes it easy for you to figure out the best route. You know which line to get on and which transfers you’ll need to make.

The map does not exactly correspond to the real world. The stations have been moved slightly, this way or that, to make the individual subway lines straighter and more easily distinguished from or associated with other routes. In other words, the map makers have taken a bit of license with the truth to serve the needs of people while they are using the underground system. You probably need another map to get an idea of where a station is in relation to the landmarks around it.

You don’t want a map that’s too detailed. A map that is too detailed makes it harder for you to quickly extract the usable facts. Everything is of equal importance. A map needs to help you find what you need to find. So a tourist’s map of London might contain sketches or larger than scale images of important sights you want to see with the nearest tube station marked. If every building is included in the map then no building easily stands out.

I’m reminded of that from time to time when I’m following directions from Google maps. The directions are mostly great and tend to be correct. But the directions for getting onto and off of highways can sometimes be over detailed. I’ve been traveling to a work site this week where I get off the highway and take the left fork at an exit and curve around to the left and stop at a light. Google maps told me to take this left fork and that was a perfect piece of information.

When the light turns green I continue to curve to the left while merging onto another street. Google maps tells me to take a right onto that street and then a left onto that same street. Until I was at the intersection I didn’t really understand their directions. The directions were completely correct but over detailed. That said, I don’t know how else they could have described it. We would describe it to each other by making hand gestures and using words like “you kind of are on the road already when the light turns green. You just need to keep going but shift over a couple of lanes to the right.”

When you write you need to wrestle with this balance too. I’ve told you not to use too many words because you might lose the readers attention and not to use too few words because they might not know enough of what you’re talking about. But there’s more. If you use too many words then the reader can’t know what’s important to your story.

Rex Stout had Archie write this to begin chapter 17 in his book ‘The Silent Speaker’: “Monday would fill a book if I let it, and so would any other day, I suppose, if you put it all in.”

What a beautiful aside that captures the truth perfectly. It’s great advice to writers. Don’t describe every mouthful of food. In fact, don’t describe every meal if it doesn’t serve a purpose. So much happens in every day that we don’t need to report. You need to describe just enough that you have set the scene and then move on to the important bits. Probably, more accurately, start with the important bits and every now and then step back and paint the surroundings.

Even if you’re writing about technology, there are so many pieces you don’t need to describe. After I’ve taught you the syntax of a language, I won’t remind you to type an opening curly brace and hit return to start a method. I’ll assume you can remember that part.

Whether you’re writing fiction, non-fiction, or a how-to book, don’t just give me an aerial shot of your subject. Figure out what it is that I need to know and how I need to be told so I can best navigate what it is you are telling me. Give me the London Underground version.