Whatever the world you build, if you have humans or humanoids, likely you are going to have more than one race. While you may be completely familiar with your own race, you may not be thoroughly so with ALL of the traits of other races.
With this in mind, I hunted down a bunch of resources to aid you in understanding and developing races for your fictional world, based on real life examples.
The first source I found is a basic definition of race, what makes races different, and a very basic description of each race found among human kind here on earth.
The second source I found is the Stanford Encyclopedia of Philosophy. It also gives a brief definition of race, but it then goes into the following sub-topics on the matter:
1. The History of the Concept of Race
2. Do Races Exist? Contemporary Philosophical Debates.
3. Race versus Ethnicity
4. Race in Moral, Political and Legal Philosophy
The third source that I found was (not surprisingly) Wikipedia. What is interesting about this, is that it defines and explains Race as a human classification system. This is exactly what Race is, but it’s interesting to have it put so plainly. http://en.wikipedia.org/wiki/Race_%28classification_of_human_beings%29
The fourth and final source I found was http://www.sociologyguide.com/types-of-society/race.php
This source also commented on the issue of prejudice and superiority, debunking it by explaining the way that certain traits are acquired.
Between these sources, you will have all of the information you need to determine the traits you wish to use in your characters development for your story. There will be social aspects to take into consideration as well, so be sure to spend time developing some depth to the cultures of your characters as well.