Find a dark area where you can move around freely.
Place your camera on the tripod and situate it so it is pointing at the dark area where you will be creating your light graffiti tag. A tripod is not required, but when doing long-exposure photography it is helpful to have the camera set in a stable position.
Set the shutter speed on your camera to a long duration. Shutter speed controls will vary between different camera models, so check your camera's instruction booklet if you are unsure how to adjust the shutter speed.
Stand in front of the camera with your light source.
Use the self-timer function on your camera or have a friend press down on the shutter button. Move the light source around in front of the camera to "draw" your light graffiti tag. Continue moving the light source within the space captured in the camera's viewfinder until the shutter closes.
View the photographed image. Adjust the shutter speed and aperture settings to experiment with different results.