Now that you know what kinds of people populate your world, and have an idea of what they might look and act like you can begin to build your characters.
Me, I let my characters come out as I write the story. As long as I have a general idea of what they look like, I run with whatever comes to mind. Some writers actually do character sheets, where they draw out every little quirk and characteristic of their characters. From their hair color, right down to their favorite snack of chocolate covered sardines. XP
If you're like me, you keep all the character information in your head, but, if you're also like me, you sometimes have so many characters in your head you have trouble keeping them straight. Especially if you're like me and work on more than one story at once.
Even though I don't always like to, I will sometimes use a basic character sheet, although most of the time I just use a list of my characters' names. My character sheet looks like this:
Favored weapon (If applicable):
Birthmarks, moles, tattoos, or other identifying marks:
You'll note that the last two are fairly broad categories. This is where I try to flesh out something of my character. Stuff that you wouldn't see with the general description I start with. In those places I like to put stuff like, if the character tends to be a bit of a know-it-all, or if they have a "hair trigger", or if they flip their hair a certain way. Little things like that may not come out when you look at your character, but should come out when you write what your character is doing in the story.
It is in the last two categories where knowing the different kinds of people, and having them defined, also goes. This is where I put if they follow the norm of their race, or if they go against. Say my character is an elf, in a world where elves and humans don't get along at all. Under temperament and habits I would note if my character was more likely to stand on the side of a human, or if they would side against a human. Some little things may or may not come out in your story, but the bigger things, like how they might act around another race, would, and it can be a benefit to have them all written down in one place sometimes. ;-)