Reddit reviews World Builder's Guidebook (Advanced Dungeons & Dragons)

When I started making my homebrew setting back in the late 90's I used Richard Baker's World Builders Guidebook to help me design everything about the world. This book is phenomenal and will help you lay out things that you might not be thinking about, like size of the globe and weather patterns. Yes, the best advice is that you can follow is to remember that you do not need to complete the entire world when you start to design it, but from my perspective it helps to have a skeleton framework to build on when you do start out on that world.

In addition to the advice that others have given, I would recommend the World Builder's Guidebook Yes, its old! But have yet to see a resource as thorough and useful. Most of the stuff from there is not related to game mechanics so it is nice and easy to adapt to pathfinder.

Also, for me personally I prefer to start with a map and work from there. I have been using my setting since around 1995 and it all started from a few maps and has grown since then. I imagine locations, and ideas for the countries, settlements, and their history come from there. YMMV.

You can get it on Amazon, but prices vary pretty wildly.

New copies are $100 minimum.

I find the 2e World Builder's Guidebook to be a great help.

http://www.amazon.com/dp/0786904348

Check out the link below. It's a series of articles written back in the late '90's for the old "Dragon" Magazine based on helping new DM's create their own world. There's a lot of awesome ideas here. While written with the 2nd Edition in mind, the advice presented is universal.

http://www.darkshire.net/jhkim/rpg/dnd/dungeoncraft/

I also recommend checking out the "World Builder's Guidebook." It's also for 2nd Ed, but is another amazing resource, especially if you're starting from 0 and willing to allow a bit of random rolling and chaos to inspire and guide you.

http://www.amazon.com/Builders-Guidebook-Advanced-Dungeons-Dragons/dp/0786904348