Couple of points, recapping some of what was told already. First be sure to invest in sneak perks, muffl on the left and up to assassin's blade on the right, and get the right side as fast as possible it in proves your sneak damage. Second, ditch ANY follower. Followers once combat has been started stop sneaking and just go running in to combat. Pretty much defeating a stealth builds fighting style. Third, hit and move. If you are using a bow to take out targets you want to shoot from one location and then move 10 yards/meters away for a hiding spot when they come looking for you. They home in on where you shot from and should not track you to your new location unless spotted due to poor hiding. Fourth, as quickly as possible do the quests 'innocence lost' and 'with friends like these' so that you can get the Dark Brotherhood armour. It helps with your stealth, bow and 1H damage while sneaking and is the best armour you can get at low levels. The last piece of advice I can give is two fold. Invest in stamina over health, and strategically withdraw(run away, run away) when spotted until you can go into sneak mode again and creep back in on your targets. Ok, maybe one more thing, you make more noise sneaking when moving at normal speed vs the walk/slow speed so use whatever button is for walk on your system, pc it is the shift key, when you are moving up close to people.
Alrighty, that should cover it all. I personaly, following the above rules can take out a full forsworn camp/falmer stronghold w/o ever getting even a nick. Though it does hurt on increasing your light armour skill if you are trying to level to 81. LOL
