Lightning images are generally very stunning. They are very similar to fireworks to capture. However to capture those instant moments with a camera can be quite is a challenge as lightning is very unpredictable and difficult to judge where it will strike. It is best to attempt to capture lightning images at night time. It is essential to use a tripod to hold the camera steady. Tripods can be inconvenient to use, however they will improve your images greatly. A cable release can also be very usefull to eliminate any camera movement.
Find a suitable spot where you will have a clear view with possibly some interesting objects in the foreground. Also try to stay away from any street lights which may introduce flare into your lens.
An exposure time of around 1 to 30 seconds is generally good depending on the frequency of the lightning, you may even like to use shutter speeds longer than that. Use an ISO speed of 100 to 200, which should assist in keeping the noise to an acceptable level with your digital camera. An aperture of around f/5.6would be good as a starting point to try as the value will depened on the brightness of the lightning.
Set your focus to infinity and set the camera to manual focus. Bring a small flashlight so that you can see the camera controls and settings. Turn the camera flash off.