Let's play a game. Take the 2nd edtion AD&D Monstrous Manual (or any bestiary of your choice), and randomly select 2d6 monsters from it using this.
For the Monstous Manual this is between 1 and 1,089 (the number of monsters in the book), or you could do it by page number if that's easier.
If you get something unintelligent or of animal intelligence, imagine an intelligent version.
These selections are the dominant intelligent races of a campaign world. You now have to figure out how to build a setting around them.
I got 6:
Jackalwere, beaver, sirine, ankheg, wererat, satyr. I'll talk about a campaign world idea based on them tomorrow.