Step one, from Rob's guide:
1. Using one page sketch a world or continent mapI actually started with a concept phase before step one. My main source of inspiration for this campaign setting is Iron Maiden's Seventh Son of a Seventh Son album.
I like the arctic setting and the weird, desolate fantasy the album evokes for me. Based on that, I decided on a northern continent for my map.
Next, I gathered some reference material. I want to create a realistic northern medieval setting, so I chose two history books: The Middle Ages and Viking Age. I also chose some Norse mythology books, and for mapping, Jared Blando's How to Draw Fantasy Art and RPG Maps.
You don't need to go to this level of research, but I find drawing from actual history and myth gives me a ton of ideas that I would never come up with myself. There are all sorts of little details you can steal from history books.
For my continent map, I got a vague sense of where I should place mountains and things from Rob's guide, then just started drawing. All you need for this map is to place in coasts, islands, mountains, hills, forests, rivers, and lakes. I spent a lot more time on it than I needed to, but the more beautiful I can make my campaign map, the more inspired I'll feel about running the campaign.
I think I'll call this icy setting Rimeland.
Next up, Part II: labelling important regions and inventing some history.