9) If there is more than one type of people, how do they interact?
Yes, this relates back to question 8, but it is such an important piece to the puzzle that it merits it's own discussion.
Let's go back to the humans and elves from the discussion of question 8. These are considered two very different types of people. Humans tend to be driven by technology and the desire to possess more than another. Elves are the opposite, sharing all they have, driven by nature and the protection of the natural world.
Looking at these two peoples you can tell there is some major conflict brewing. Here is where you can center on social conflicts to drive your story. For whatever peoples occur in your world there are several important questions to ask.
1) Are they friends, or foes?
2) At war? At peace? In the process of bringing about peace?
3) Does one not know the other exists? (Elves are myths and legends to Humans and vice-versa)
4) Are they two completely separate societies? (Each knows the other exists, but they have little to no interaction)
5) Do they exist in one society, equally or not equally? (Elves slaves to humans, or humans slaves to elves.)
The answers to such questions can help define the plot of your story and help develop your characters' ideas and opinions.