Kiting means running away with an enemy trailing behind you like a kite. This is done to either keep it busy for strategic reasons or to kill it slowly with damage over time skills. It is one of the most effective and useful techniques a lock can use. It allows you to basically kill as many enemies as you can without ever having to stop moving or take any damage. You can destroy enemies that are far above your level and kill things that would be able to 1 hit kill you. This takes skill and quick thinking, but it's a lot of fun.
First of all I highly recommend affliction spec for this. It gives your DOT skills much more power and makes this far more effective. It will also give you curse of weakness which makes it far easier to do. Secondly I recommend shadow damage based gear. This will put more damage onto the enemies with each attack. And most importantly I recommend run speed enchants to your boots. This keeps you safely out of reach during the process.
The first step is to plan out a route. You want to find a place where you can run it around in circles without bumping into anything or letting it get close enough to hit you. Once you have the course plotted out in your head, you can start attacking it. It's usually easiest to start with a curse of weakness. This will get the enemy to start chasing you, at 70% normal speed. Keep this curse on at all times and it shouldn't be able to catch you.
As soon as you get it mad, immediately turn and run, but keep it selected. Get it to chase you around in a widely arcing circle, keeping just far enough from it that it can't hope to catch you, but not far enough to lose its interest. As it chases you, put on a corruption and siphon life. These will constantly chip away at its health as it runs around helplessly chasing you.
If it gets too close, you can fire off a death coil to confuse it long enough to put more distance between you. You can life tap as you run and allow siphon life to slowly replenish your HP. Watch the DOT timers and as soon as one of them disappears, put it right back on. DO NOT let curse of exhaustion fall off for long or it may catch you. Be patient and alert and just keep running around until the enemy falls.
If you have run speed enchants on, you should be fast enough to keep a good distance between you without needing to rely on curse of exhaustion. If you can do without it, you can use curse of agony instead to do much faster damage. I use this on my lock and can kill enemies after just a few seconds of chasing me.
If you are running in a straight line, you can technically get by without run speed enchants or curse of exhaustion. Just be warned, you can't stop for a second or turn corners too tight or it will catch up to you.
This technique is great for soloing elite enemies you couldn't normally kill on your own. It also works just fine on horde that don't have good ranged attacks. Warriors, paladins, rogues, and shamans can be successfully kited this way. I have killed 70 warriors in very good gear on my 63 lock this way.