Go to Leyamin and go to Rosentia Gallenus's house.

There will be four Scamps following her around, pick which skill you want to level up, but always be in sneak.

Go around the back of one of the Scamps so they cant see you and attack it, this way you can level up your sneak and another skill, I recommend training all the skills I said.

Note: if you are low level bring some healing potions because the Scamps will attack you back. And be careful not to hit the women or she will attack you and the guards will come after you.