While I'd love to actually be more in depth, I'm afraid I'm really simplifying the science behind the climate and terrain. It's a fair bit more complicated than what I've done, but this is still a good abstract, even if my drawing skills are really awful.

I'm currently plotting out where the high and low pressure areas are. I understand the wind goes from high pressure areas to low pressure areas, and that the rotation of the planet deflects the wind direction.

The wind coming in from over the oceans should contain moisture that will be lost as it travels further inland, and/or hits a mountain. This should tell me where my rivers and lakes will form, and where my deserts will be.

I can then mark them on the map, and hope that someone with better drawing skills than I, takes pity on the map and helps me paint in the terrain.

That's where things get fun, as I need to work out what races are where, and how did they spread. Most likely up and down the river systems first.

The general plan is that if the map is more or less scientifically plausible, I can make a plausible world (or rather 4 worlds) for adventuring in.