Right after launching World of Warcraft for the first time I have to create a new character, when choosing a race, how are they different and what criteria should I use?
Here is a good answer
Choose a race.
Before choosing, think of the benefits and disadvantages of the races you choose. For example, Tauren has War Stomp, which is a good stun for Warriors, and +5% health, which is also good for Warriors. Because of this, most Tauren players to Warrior, Death Knight or Feral Druid. However, with the case of Night Elves, Stealth is a kind of disadvantage, since it overlaps with rogue and panther(feral druid) abilities. Therefore, it can be seen as "wasted". Search on Google if you want further information.
It's usually better to decide first on a faction, then on a class, and last on a race; but it's not necessary. Be aware, however, that
not all classes are available for each race. An example of this is
the Druid class. Only Night Elves or Worgen (Alliance faction) and Tauren or Trolls (Horde faction) are able to be Druid class. If you have already
decided to play for the Horde as a Druid, you have no other options
but to play a Tauren/Troll. Draenei and Dwarves are the only Alliance race that can
play as Shamans, and Blood Elves and Tauren are the only Horde race that can
play as Paladins. If you decide on a race before you decide on a
class, understand that your options may be limited.
Consider how would you feel playing a certain race. Remember that you will spend months and maybe years watching your character from his or her back, so keep that in mind when picking a race. For example, you may find Gnomes' movements and voice a little annoying, Undead characters' bones poking though their armor a little disturbing, or Orcs' roughness a little unpleasant.
There are two ways I use to help me choose a race for a character.
Performance - All races have abilities and passive benefits that make them better at doing a certain job e.g. tanking, At being a certain class, And there are some races that are better at being a certain class spec than other races. This is often quite an advanced way of selecting a race and is focused on being the best at what you do during your end-game experience i.e raids, And I wouldn't recommend it to a new player.
Preference - This is the method that I use more often and would recommend to a new player. This just involves what you prefer i.e character appearance, racial background, roleplaying etc. This method is also helpful when your more focused on questing because the race you pick hugely influences your level 1 - 60 levelling experience for example if you're a Blood Elf it's very unlikely that you'll do your 1 - 10 levelling in Durotar.
For you I would definitely recommend the second method but feel free to use the first one if your eager to level quickly and advance to the later level experience.