This Glitch allows you to level up several of your stats as well as actual level.
Ones Raisable : 1 handed, 2 handed, Archery, Destruction, Sneak and Restoration.
In order to do this glitch travel to Riverwood, then look for Alvor and Sigrid's House. (Blacksmiths house)
Go inside and look for Hadvar.
When you see him ensure it is just you and him around. Then Enter Sneak mode and proceed to utilise the skills you wish to level up.
He is immortal and will not react besides falling temporarily when out of health. I.e. No aggression to you or calling the guards.