Im sure this has been posted lots of times...
to get to hyjal go to winterspring
1.fly to winterspring
2.go to the bottem of the map that seems to be touching the rim of hyjal
(Note: Dont be a gnome when doing this... its super hard then)
3. find a piller on the wall to your right when you get to the end of the cave of the place thats touching hyjal
4. jump on the right side of the piller
5. use the wall jumping method... wont work when on mount
6. walk around the rim when ur up
7. jump up the wall again exept stop at where t looks like this /\ sorta...
8. jump on the ledge.
9. go around the tree and turn left...
10. go on the platforms one by one... find ways to get up a few then jump up on the mountain
11. if you fall in hyjal and ur stuck behind a seal dont worry... just jump up the seal using wall jumping method
(Note: if ur a mage you can blink through the seal)
12. jump down into hyjal and keep goin... youll hit another seal... just keep going and then ur in... it will say discovered hyjal when you enter...
(Note: I have done every glitch in the game... i know my glitches/exploits)
good luck doing this...