I need more than that. Is this a world map, a regional map, a city map, a unique wilderness map, an underground or undersea map. What specific terrain do you want to include: seaside, mountainous, desert, etc. These general questions need answered. Each of these are very different kinds of maps and each have different approaches. If I'm going to create a map for a European analog region of kingdoms on a major part of a continent, I need to know where are the mountain ranges, what is the climate, what kind of tectonic plate activity is going on that create the larger terrain features? Again, depending on the kind of map you're trying to create determines what kind of information is required to do a proper job. I guess you need to do some brainstorming ahead of time.