How to take pictures at night without using the flash?

I have a nikon D90. How do I get clear shots at night without activating the flash or the light on the camera? What should my apature, shutter speed, and ISO be at, and what camera setting is best?

At night the light levels are low so in order to get enough light to make an exposure you need;

- a wide aperture (low f number) - most consumer lenses don't hae wide apertures, you need f2.8 or wider.
- a high ISO - but leads to noise
- a long shutter speed (need a tripod)
- to add light (ie use flash)

The person below is spot on.those tips will help you capture a photo in the dark without flash

There's no one-size-fits-all. Depends where you are and what you are shooting. In town? Out in the depths of the countryside?

Out in the street there's a lot more light that you would think from buildings, streetlighting, vehicles, the moon.
You need a sturdy tripod and a cable release so you don't shake the camera while pressing the shutter.
Select manual mode
Turn off the image stabilisation
Manual focus may be better than auto
set ISO to 200 or 400
set your aperture to get required DoF
spot meter on a bright area and reduce by 2 stops, maybe 3
shoot!

examine th eshot and adjust exposre accordingly