Junglers you have to do this
When you go to gank and the gank is successful, dont just take a couple of minions and back to base or go back in your jungle to kill jungle camps for gold and XP. After you get the kill at mid, top, or bot; be sure to push in the next wave or 2 to make sure your minions go into their turret. DONT kill the minions because you will get the gold and it may piss off the laners causing them to tilt. What you want to do is help them shove by getting the minions low so your laner can finish them off and get the money while you both share the XP for shoving. The XP you get for shoving is so much better than jungle XP.
If you do this, its possible to get to lvl 6 a minute sooner than you normally would if you just ganked then left. If you get to lvl 6 a minute sooner you will be able to gank the enemy bot lane while they are still lvl 5 and it will make your ganks very efficient. After that gank do the same thing (shove the lane) and then you will be snowballing.