How to do light graffiti with Nikon D3000? - 1

I have set my ISO to 200
My aperture is 3.5 and shutter speed is 1/30 and my timer is 20seconds

What am I doing wrong?
Btw, it was set on auto.

In a dark room, I set the aperture to the largest setting, set the shutter to bulb or a given number of seconds, aimed the camera at a wall and used a laser pointer to "write" on the wall.

What are you doing wrong? Well actually several things.

ISO, fine at 200
Aperture, wide as it will go.
Shutter speed: At least 5-seconds perhaps 10
Self timer at 10-seconds is fine.
Tripod?
Get off of auto and go to manual.

You need to shoot using much longer shutter speeds, like from 30 seconds to a few minutes. You will have to place your camera in the manual mode to do this

To do that you need a remote shutter release to lock open the shutter for as long as you are writing your graffiti.

The problem is you're not using your brain, using auto mode is fine, but don't just blindly follow it.

Your shutter speed is 1/30 of a second, think how long a second is, then divide that by 30. 1/30 is a very short time. Light trails are simply moving light sources, now consider what that means. A fast shutter speed will catch a fast moving object, and a slow moving object needs a slow shutter speed.

Depending on your focal length, and the subject you will need anything between 1/2 and a number of minutes.

Go to YouTube and search on photographing fireworks.

The technique is very similar, except for the possibility of the shutter speed. You may have to change it somewhat, but don't be afraid to experiment with different shutter speeds.

Start at 20 seconds or so, and go from there. If you have to modify the exposure, you can balance aperture/ISO/shutter speed until the shutter is open long enough for you to get the light trails, but still get a properly exposed photo.