1. The tools
Besides your camera you will need a tripod and a torch (or any other kind of light you can handle and move). Why a tripod? Because you will choose a shutter speed slow enough to do your drawing. In my case, it usually takes me 20 to 30 seconds to create the scene.
I recommend using a remote control which gives the option to lock the shutter in bulb mode. Like that, you have all the time you need to be creative! I use the Nikon MC-30 with my Nikon camera and it works well.
All kind of lights can be used. Don't worry about your sensor, it won't be damaged if you point the torch (laser etc) directly on it while you shoot.
I use a little light also used as a key chain. It s powerful enough to draw the characters and can be turned on/off just by pressing a button.
3. Camera settings
Shutter speed: As long as you need to create the scene.
ISO: I usually put it on 100 so I can set the shutter speed on a very slow value and I don t get any noise on my photographs.
Aperture: Set it doing a test shot without drawings, focusing on an element close to what you are going to draw.
Flash: Can be used to fix a person or a moving element in the scene.
White balance: Set it doing a test shot. Street lighting is usually yellow.
Focus: Obviously on manual if there is not enough light.
Light is your friend, you could use moving lights from cars etc.. for exemple, I did one while a train was passing under a bridge.
Wear dark clothes if you want to lower the chance of being visible on the photograph.