I am working along the lines of Thessilian, most of my work just starts out as a doodling of a landmass and such, and then I refine it a bit more and try to make it better and better.
While I did some commissions for free a while bakc (that can be seen in my sig) I found that while it was a good way to learn new techniques, but often people wanted things that conflicted with what I feel is a natural world (like a continent made from half ice and half tropics and sutch, rivers going upwards because they did not originally think of topography and sutch) that it somehow felt "wrong" not to correct such..

On dungeon maps I do pretty mutch what Thesslian does.. design them with the inhabitants in mind.