In each faction there are five races to choose from. The Alliance races are: Draenei, Dwarves, Gnomes, Humans, and Night Elves. The Horde races are Blood Elves, Undead, Orcs, Tauren, and Trolls. Each race will have different racial traits and specializations that will benefit you in game. There aren't really too much differences in the traits and other differences in the races except for looks and faction. Most players already have a specific race that they want to play when they start the game, and you simply need to go through them to see which one appeals to you the most.
Also some races will allow you to play certain classes of toons and others will not. For example, the Paladin on the Horde side can only be played with a Blood Elf, yet on the Alliance side it can be played by a couple of classes. And, the Shamans can be played by several different races on the Horde side by only on the Draenei on the Alliance. So, look through the different races and see which classes are offered for that specific race. (We will go through the different classes in the next part of this mini guide so you will be able to see which one appeals to your gaming style best.) As you level your toon up, the racial differences that the tiny buffs give at the beginning won't matter much at all, and the only difference will be in looks.
Each different race will have a different starting zone, except for the Alliance Dwarves and Gnomes and the Horde Orcs and Trolls, they start in the same faction starting zones. Now, keep in mind that the Alliance and Horde distinction is a massively important one. You won't have much interaction with the other faction in the starting areas, but as you progress through the game, you will cross paths. You will be teased, spat upon, called a chicken, and more, especially if you are on a PvP server.
Overall, race comes down to your chosen faction and which one appeals to you the most. So, you want to play the race that you prefer and not based on the tiny buffs that are offered at the beginning of the game. In the next part of this mini guide, we'll go through three of the main classes: the warrior, rogue, and the hunter.