Yea. Easy. Go into a dark corner of a shop in the Imperial City. Sneak. Put a rubber band around the analog stick and another part of the control so its stuck in that position and forcing you to walk into the corner. Also, obviously make sure the shop keeper doesn't see you. And now you can leave the room and come back when you're at 100 sneak, or if it's one of your major skills, you can come back and level when necessary.
If it's one of your major skills, then I wouldn't worry about it too much. Just sneak around before you kill enemies. If it's a secondary skill, then just sneak around in a room where someone is sleeping.
If it's a major skill and you level up your character mainly through non-combat skills such as sneak, then your blade/blunt, blocking, and other combat skills will obviously remain low until they are leveled up. This can become a problem. As you level up, so do the enemies. So if you have are lvl 20 with 100 sneak and 25 blades, you will have a harder time killing enemies than if you had 60 sneak and 60 blades at lvl 20. (I'm just using random numbers as an example).
If sneak is a secondary skill, then it won't matter.
If you want to actually level up sneak the active way instead of doing it the "lazy" way and wasting precious agility points for later levels, then you must do something all the time for all the missions you plan on doing.
If there are people/monsters in your way during missions or just hanging around, try going in sneak mode. If they are in your vicinity and the eye is dark, tap the stick (it's W for me, since I have PC). The trick is that your sneak skill levels up MORE if you are sneaking while NPCs are around and cannot notice you. Doing so will increase your skill by 50/level points per second, rather than sneaking alone doing 10/level points per second.
Attempt to pickpocket the NPC if you can (the best way is to save and do trial and error). A successful pickpocket is a whopping 200/level points per successful steal. Obviously if you were able to grab someone's gold at skill level 5 (which is near impossible; I know I've tried), you would automatically advance a skill level.
Someone else's sneak skill also plays into the game. Find an S-Tard, which would be anyone who is Sneak inept. These are usually Warriors, Knights, Mages, Battlemages, etc. Basically anyone who is clearly not of the Stealth-based. A beggar would have an easier chance of catching you take their meager pockets than a town guard would, because beggars aren't fighters so they have more points towards sneaking, and because town guards ARE fighters so they put their points toward combat skills.
Doing these steps will make your character level MUCH faster.
Golden rule of thumb: Never pickpocket Chancellor Ocato. In the middle of the town. Next to guards. In the day time.
Well yeah, if you're level 30 with 100 sneak with chameleon equipment! Is this going to work in earlier levels? Hell no! XD
100% chameleon = cheater. You probably don't have this Wex, but it really is. It's basically a full invisibility spell where you can still attack and activate without losing the effects. cheeeeeeeaaaap...
Anyhow, to rise quickly in stealth, you've got the perfect spot in the tutorial, near the first enemy you're asked to pass by using stealth. There's an hidden corner where you can stay all along.
By the way LV 27, 60% chameleon. More than enough.
