For doing maps these days, I draw them using a free piece of software called Mapping Board.
It was originally designed for doing maps for Command Decision scenarios, and a feature I really like is that it allows for both square and hex grid overlays (as I play a lot of grid base games).
Before that I used to laboriously draw them in MS Paint.
If I was on a different device, I’d embed a link.
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke