I really think it helps to be somewhat artistic in the drawing department to be good at light drawing and light writing, which I am not so i've not really bothered with it before and the reason why I do not have any examples to show but google is full of inspiration for it. It can be great fun though and great for kids to do as well. Pick any subject and draw! simple as that, any light source will do, some torches will be far too bright so a small dimmed light often works well. A good starting point is either find some graffiti on a wall that you can trace around or get a car in a dark place and trace around the countours.
If you're getting serious about light drawing it will help to draw your idea on to paper first to plan out because although you are drawing with the light you can't see where you have been making it quite easy to make mistakes.
Again not my strong point personally, helps if you can write neatly. A lot of graffiti artists do well in this area because of their hand control. Write anything you like, your name is a good place to start, two ways of doing it, one is to face the camera head on but you will have to write backwards or it will be reversed in the image, or face your back to the camera turn your torch round and draw and write or you would on paper.
Exposure wise I would treat it like a standard long exposure, leaving time for the sky and other areas to burn in and possible add some extra lighting too if you wish, and If I ever do a light drawing or a light writing you'll see it right here.