Can someone please inform me on how to perform a stealth kill? You know, like when you sneak up behind someone quietly and slash their throat with your dagger. Everytime I try to perform a stealth kill, I just slash them in the back and attract the attention of the omniscient city guards.

Im pretty sure theres just a bunch of variables that need to be fulfilled, like obviously not being seen, being able to 1hitkill them, having the right angle aswell, the right distance to target and so on.

I find it happens 70% of the time for me when the target is standing upright and I can get directly behind him/her.

Just sneak up behind your target without being seen (pickpocketing distance) and hold down the right-hand button, whatever it is for your system. (i.e Right Trigger for 360)

Sneak behind them with a dagger...if it can kill them normally, it will usually execute a throat slitter. You must remain undetected the whole time during the kill, and if you do, it will be a stealth kill. I murder windhelm guards and toss their bodies into the river all the time using a blade of woe and 12x bonus.

I hate when they are in a high backed chair. I sneaked up some vampire master and he was sitting in the chair, i'm crouched there right next to him trying to get an angle of an attack. I eventually gave up went a distance a way and shot him with my bow. His crappy AI allowed me to kill him with ease since he was too dumb to find me.

Ok thanks. Can you only stealth kill with daggers? Or can you stealth kill with swords too?

from what i've seen, it only happens if you do enough damage to kill your opponent in one strike, you get a neat throat slashing animation which can be in first or third person, happens every time.

Killing enemies in one hit isn't too hard either, assuming you're perking right, yor best help is the one in the sneak tree which causes daggers to do 15x stealth damage (I took a sleeping dragon down to almost half health with that), might not be a bad idea to upgrade your dagger with blacksmithing if you can, and perhaps enchants and/or poisons if you're still having trouble. All else fails, lower the difficulty.

It can happen with a sword.

Power attack in stealth while behind them for best results.

Ok. That's good to hear.

I have a Daedric Sword that does 88 Damage. If I can get the 6x Damage for Sneak attack this target is toast.

UPDATE: Yes! I did it. I can confirm that to perform a stealth kill with a sword you sneak up behind target and hit power attack like Ravenius said above. Thanks for all the advice guys, this is what a forum is for.