The Gee Whiz Factor: Initially just about any light painting picture will look good, but after some experience you will become much more critical and less accepting of merely random or overly regular designs.
Shooting Blind: Unfortunately, today's cameras do not show you the image as the light is accumulating with a long exposure. In addition with a single lens reflex or LCD viewfinder, the viewing system goes blank while you are taking a long shutter speed exposure. You are, in effect, shooting blind. I find that if you view with one eye and then switch to the other eye as the picture is being taken (to see the scene with your eye), that you can do quite well.
Variety: Look for places where there are a variety of lights. The color of these lights become the colors that you will be working with for that photograph. Also look for different intensities of light, such as bright and dim along with reflections (as mentioned earlier in this tutorial).
Flashing lights have a quality all their own. In a moving car, for example, a flashing yellow stop light will produce a series of yellow dashes. In other situations the flashing light, because it is only on intermittently, will be of a lower intensity.
You may get something totally unexpected. When this happens, pay attention as you may have discovered an entirely new effect. Most lights, for example, will smear, but others will turn into sharp multiple lights (such as this Ferris Wheel photograph). This can be a very dramatic and unusual effect.
Focus: While many successful images will not be sharp like traditional photography, you will, nevertheless, want to focus as accurately as possible on your light sources. Generally you will want sharp points of light to 'paint' with, not blurry ones. A good technique is to turn off the auto-focus and set the camera manually to infinity, assuming your lights are approx. fifteen feet or more away. Also be aware that focus is less critical when shooting with a wide angle setting; yet it can be quite critical when using a telephoto setting.
Hyperfocal Distance: This odd sounding term is an extremely useful setting if you know how to set your lens properly. It is a simple way of getting the maximum clear focus for any focal length, from a near point to infinity. It means simply this: you set your lens to a close distance (the hyperfocal distance) where everything is in focus from that point to infinity. Clear focus will also extend several feet closer to you from the hyperfocal distance as well. A hyperfocal distance exists for every focal length, although it will be much further for an extreme telephoto setting than for a wide angle. In light painting, you can set your camera manually to this setting and then forget about the focus until you change the zoom setting on your lens.
Combinations: You can combine different camera movements, stationary sharply focused objects, relative sharpness and subject movement in just about any way that works. This is uncharted territory and begging for exploration. Enjoy!
In this example, you can clearly see the hood of this old Chevy in sharp focus, and the streaming street lights in the same picture. This happened because the car was stationary relative to the camera (that was mounted on the dash) but the camera was moving in relation to the lights.
The rain drops on my van's windshield were relatively clear since the camera was stationary relative to the windshield, but the street lights streaked as I drove down the highway.
My wife is relatively sharp in this photo because the camera is stationary in relation to her movement (even though she is being jostled around a bit as she drives). However, the lights outside the car are quite blurred because the camera is moving in relation to those lights.