Interesting note, there isn't exactly a world map or digest for D&D's setting "The Forgotten Realms" the way there is for Pathfinder's "Inner Sea", and I would really like to make my own world for them to explore instead of something they could just read about on the internet.
But of course, I hate putting a lot of work into a world knowing that my players may only see a small chunk. Or making a new world for the same fantasy setting, etc. So I made a compromise. I am only ever going to make one fantasy world for D&D (and maybe even port it over to Savage Worlds).
Well, lets start with the world map and I will explain as I go. I went over to Donjon and used their World Fractal Mapper. You could draw the coastlines by hand if you want. Then I blew it up to 15" x 30".
Note that this is just the land masses. I wanted a lot of islands and continents for my world to explore.
Then I chopped off a segment (7.5" x 10") and printed it out.
This is where my Party will start. I won't draw towns or geological features until they come up in game. My party started in a Village and had to cross a mountain range in their first adventure so I will mark the village and draw the range they had to cross on the printout. I'll just keep creating adventures where the party wants to go and fill in the map afterwards, that way there is no wasted prep! When this region is done, I will transfer my sketches onto the main world map.
Why keep track at all? In case I or the party wants to revisit a location they had been to before, like their home village, or a haunted keep they couldn't tackle the first time.