Either go to High Hrothgar or the Throat of the World (the latter you can get to by climbing on the rock faces of the mountain at any point) and either sneak attack the Grey Beards every five seconds or do the same with Paarthurnax.
The World's Most Interesting Man: I don't always herp, but when I do, I derp.
Sometimes, I also follow those random persons you see on the road, like the farmer going to join the Stormcloaks, or the pilgrim going to the Shrine of Azura, or the party going to Vittoria Vici's wedding . Just follow them in sneak mode .
Go to Hags End, with either 2 plates or the Ritual Stone. Reanimate the dead assassin, or plate through the wall and strip him of his Ancient Shrouded Gloves and Boots, then sneak attack your way through a few Nord ruins. If you also get the backstab perk, that's 12x damage per sneak attack. Levels Sneak pretty fast.