Here are easy steps to instant leveling to 90!
Step 1: Heirlooms
Always have a weapon! Heirlooms weapons give great stats at low levels which help you do good DPS
Step 2: Class Spec
Tanks often get 1 second ques in dungeons but like 20 minute ques in raids
Healers are rare in some realms. It is easy to get into a dungeon or raid fast as a healer.
PvP is all the same with DPS, tanks and healers I have found.
Step 3: Dungeon
Healers are key in dungeons. If you are lazy just be a healer and do nothing. Just be sure to keep everyone at around 80% health all the time
Step 4: Ding, Level 90
Good luck in Azeroth and you can find me in Baelgun as a human warrior named Jolapo (alliance)