First of all, there's no "best class" at all, because each class has its specific positive and negative aspects compared to others which is really important for PvP balancing.
Did you ever play any RPG or MMO? If so, do you prefer melee or ranged chars? Would you like to invoke creatures that help you while fighting or do you want to fight on your own? Would you like to either pick the role of a damage dealer (DD), Tank or Heal? These are some basic questions that you should try to answer before making any decision.
Here's my personal attitude towards classes:
I suggest you to get started with the Hunter class if you prefer playing ranged. The hunter is very strong and deals a huge amount of damage and is usually not attacked during PvE (Questing) thanks to his tanky companion which usually pulls the mobs aggro. I have a Level 90 Pandarian Hunter, and I still love to play him.
I hope that I could be of help, if you have any other questions, feel free to ask