Lightning bending is the ability to control and summon electricity in any form. The hardest form of this is summoning and directing lightning. Because lightning is a very powerful form of static electricity, benders need to start with smaller amounts of energy and work up from there. This skill is very hard to learn when using larger amounts of electricity, but fun and practical after the bender becomes more acquainted with the feel of it.
*NOTE* It is not recommended that beginners try more than the first technique listed here. Lightning bending is very dangerous if it's not being handled in a cautious way.
The first and easiest technique to try for the beginners is the electric touch. The effect will be, when done correctly, the ability to use Chi to shock something or someone by touching them. (Almost like a carpet shock, but stronger and commanded). First, focus very hard and meditate for a while until you feel ready to really pour everything you've got into this. That way you will have a shock strong enough to feel within the first few tries. Concentrate on your hands, specifically on your finger tips on each hand, such as the index fingers. Pool as much Chi there as you can without being uncomfortable about it. Then start to move the Chi around in a flowing motion faster and faster inside those two fingers. Build up as much speed as you can while keeping the Chi confined to the fingers. Then imagine it to start crackling and snapping. Imagine it to start jumping instead of flowing through your fingers. At this point you should definitely feel a strong tingling in your fingers that you are pooling Chi in. Then when the feeling is making your fingers twitch and spasm, bring your fingers together and visualize the Chi from both fingers meeting and exploding in a controlled collision. You are completing a circuit by touching your fingers together and quickly combining positively and negatively charged electrons in the form of Chi. This is the same thing that causes lightning in nature. After much practice you will be able to control the strength of the shock, and also learn to complete the circuit with another object, allowing you to shock something else without feeling the recoil shocking yourself.
This intermediate technique will allow you to create a larger ball of static and make a much stronger shock. This technique takes a LOT of Chi, so do not attempt it without having some experience and strength in other areas of bending. Start out with the electric touch technique, but instead of pooling Chi in your fingers, build up the Chi in your entire hands. Fill them until you feel a very strong "warning" indicating that it would be unsafe to pool any more Chi. This "warning" can be large spasms or anything else, you'll know what the warning is when you feel it. Then use the same images that you used in the electric touch to make the Chi move faster and faster and crackle with life. Once it feels as strong as it did when you had results with the beginner technique, bring your hands up in front of you so that it looks like you are praying, but leaving at least 5 inches between them. Then visualize the electrically charged Chi jumping back and forth between your hands moving so fast that it becomes a solid flow. Then cup you hands slightly, and try to stop the Chi from flowing and form it into a ball between your hands, while still keeping it crackling and snapping. You can do anything with the ball after enough practice. It will take many attempts before being able to keep the Chi charged to such a degree without actually touching it, but it will be worth it after you have mastered this. You will eventually be able to "shoot" the orbs at targets, shocking them from a distance. Also practice forming the statically charged Chi into other shapes and sizes; this will increase your control over it and allow you to make stronger static orbs.
Once again, lightning is a very dangerous technique if you don't pay attention. Only start these techniques when you feel you are ready for it and be sure to meditate first.
It might benefit if you (or someone with you) know healing, so that you (or someone with you) can heal you if something goes wrong. However, having a healer (especially if your healer specializes only in papercuts) does not make you impervious, so be careful anyway.