Writing when people read out of necessity

When people read out of necessity, they need something different from when they read for pleasure. 

For instance, if you were reading out of necessity, which of the following would you prefer:

The device by which one might quench the raging flames of an inferno is perched unobtrusively above the cooling apparatus.

OR

fire extngshr abv fridge

Both have shortcomings.

But most readers prefer the second version because they can extract the main message more easily. In a situation where someone would need to consult that piece of writing, the first version asks too much of the reader.

 

So how should we write given that many of our readers are reading out of necessity?  Our writing does not have to be perfect. But it should allow them to easily find and grasp the essential information they need.

 

Image by Simon Q from United Kingdom [CC BY 2.0 (https://creativecommons.org/licenses/by/2.0)]