Light painting means 'painting with light'. You can use any light source, like your torch, to draw anything you want, and record it with your camera.
Shutter speed: Use slow shutter speed so the camera can record the movement of the light source.
Aperture: Use small aperture, so you can get a slower shutter speed, so your picture will not be over exposed easily.
ISO: Use low ISO(like ISO 100), so there will not be too much noise on the picture.
Torch(or any other light source), this will be your 'pencil'
A steady tripod
Dark places are good for light painting, like the beach at night, parks, or your room (with lights turned off).
If you want to take a photo of yourself, this function can help you a lot. It provides enough time for you to prepare, all the cameras have this function. 10 Seconds timer will be ok, if you have a wireless control, that will be great.
Also, mirror image you are drawing. For example, if you are writing 'Hi', then you have to write 'iH', so the words will show up in the right direction
Auto focus does not work well in dark environment So we have to use manual focus, Illuminate the subject of the picture, then turn the focus ring until the image is sharp. Or you can Illuminate the subject, then point your lens to it and start auto focus.
After you have completed a stroke, cover the light, then move, and start another stroke. So that the images will not all linked together.
Dark cloths avoid your shadows in the picture
Glassine paper with different colors, stick them on the light source, so you can decide what color the light is
Example 1
Diffculty: 1/5
Example 2
Diffculty: 1/5
Example 3
diffculty: 2/5
Example 4
Diffculty: 3/5
Example 5
diffculty: 4/5
All examples are shot in my room at night, with lights off, windows covered with curtains