Once you can get to Bleak Falls Barrow, go and talk to Sven to talk about his love troubles with this girl. Accept to deliver a fake letter to the girl he mentioned. Go find the girl and deliver the letter (lie) to her. After, go to Faendal and accept the Golden Claw quest. Go back to Sven and talk to him about the quest. Then tell him to follow you.
Sneak behind and sneak attack Sven. You can do this as much as you want (as long as you don't kill him). For every sneak attacks, your sneak skill should increase, which increases your level progression. Sven gets mad at you obviously, but he never tries to attack you back.
*NOTE*: DO NOT get the perk to increase one-handed weapons to do 6x damage. If you do, and you try to sneak attack after you get the perk, you'll do a sweet kill animation where you slit his throat. Sven dead = no more sneak attacks :(
You could save up your perk points after each level up to get all the weapon sneak skill perks at once. (to avoid killing Sven)
This method should also raise one-handed weapon skill (or whatever type of weapon you have equipped) as well.