Wowhead guide
Method video guide
Fatboss video guide

PoV:s (nice to watch to get the feeling of the full fight)
Frost mage
Hunter
Combat rogue
Resto druid
Prot paladin

Make sure you understand about following added mythic mechanics:
 # The Felfire Transporter vehicle
 # Increased frequency of incoming vehicles
 # 2 extra minibosses U'rogg and Grute and their abilities