The best way to take shots of lightning is to open the shutter for as long as you can, if you use any "burst" the shutter will open and close in a fraction of a second which is only used in light conditions and will probably be to fast to catch lightning. I think that your camera will only open for 4 seconds.
That’s entirely up to you, but you will get the best results in normal mode as all night mode does really is invert shadows and highlights. Plus you will tend to get more of a black and white pic that the great purple lights in lightning.
Unfortunately we don't get much lightning where I live (Cornwall, UK) so I can't really show you any examples. Do a Google image search for lightning, you will come across some very impressive pics.