Canon 400d, I need to know how i can take a great night picture?

For successful night photography you must use a tripod.

For low-light exposures I use and recommend this site:

http://www.calculator.org/exposure.aspx

I used the Scene 'Distant view of city skyline, floodlit buildings' and ISO 200 for these:

http://www.flickr.com/photos/drifter45h/4048051455... 100mm @ f11, exposure of 30 seconds.

http://www.flickr.com/photos/drifter45h/4048796836... 200mm @ f11, exposure of 30 seconds.

If you also look at the Scene 'Domestic interiors at night, subject lit by campfire or bonfire' and choose ISO 400 you'll quickly see why owning a 50mm f1.4 prime lens is desirable for available light photography.

You will need to place the camera on a sturdy tripod. Set the camera to manual mode. Set the ISO to 200. Set the aperture to around f/4 or f/5.6. Start taking shots while progressively lengthening the shutter speed until you get the shot you want.

Install camera on a tripod then set to ISO 200, 30s, f/5.6. If too dim, set shutter to Bulb and increase shutter time (> 30s). If too bright, decrease shutter time (< 30s). Work shutter from there until you get your desired results.

In very low light focusing can be tricky.

For this moonlight shot with an Olympus E-PL2 with 14-42mm kit lens I used the camera's two second delay. I shined a strong flashlight at the car's side reflector and got the camera's autofocus to lock onto that. As soon as it did and the timer started, I pulled the flashlight away so it would not be part of the exposure.

http://www.martingrumet.com/olympus60sec-iso400.jp...

For this shot with a Nikon D60 and 28mm AF-D lens I used the ability of that lens to be dialed to infinity on the distance scale in manual focus.

http://www.martingrumet.com/canada17jan09-01dawson...

Here's one that may interest you.

http://www.flickr.com/photos/jimsphotostuff/345850...

My specs.

Shutter 10 seconds

Aperture: f/10

ISO: 100.

If you're not using a remote use the camera's 10-second timer because even the movement of you pressing the shutter release will cause blur.