STEP ONE: SETUP / SKETCH
I start by opening a new file in Photoshop. Since I have no end product in mind, size doesn't really matter much, so I'll just choose 8.5" x 11" (2200 x 1650 px), and a 200 pixel/inch resolution.
Now I create a new layer called "Sketch" and there, with any brush (set at 25% flow), I just start sketching some ideas. I have a Wacom drawing tablet, so this is pretty easy, although a mouse woks too--as does a hand sketch later scanned in.
I think I'll make a fantasy map. (*sketch sketch sketch*) As I go I see I've made an island/continent with mountains that somehow appear in the shape of a dragon's tail. Neat! I'll use that. (*sketch sketch sketch*) In fact, just for fun, what if I made this an artistic map with an artistic dragon drawn next to it? (*sketch sketch sketch*) Okay, what if the dragon is more of a serpent/"wyrm" that is holding a frame of the map. Now that's neat! Much like medieval maps with angels holding the world...although not as holy.
(NOTE: If this dragon distracts you, and you're thinking "I don't want a frame around my map!"--Just ignore that part of the following tutorial. The actual mapmaking process will stand alone, too.)
Attached is my first sketch of "Thracioth," including the frame & the dragon. I think I'll name the dragon "Rob," after all my friends of that moniker on this site.