Not a veteran, but for the few maps I've made, I've done it like this (with the exception of my current work-in-progress):
1)Brainstorm/reasearch (in the case of a real life map)
2)draw a sketch of what I want, drawn to scale
3)create all the land
4) adjust water depth if nessecary
5)place bases, spawns, and accompanying items
6) add mountians, rivers, lakes, etc AROUND the bases, so you don't end up with things like ends of runways being on the water, or hills making it impossible to lift bombers from certian runways
7) draw the terrain
8) touch-up/sanding the edges