Rubbish night shots with nikon d3100

I'm 14 and i got a nikon d3100 for my birthday in August.i've never had a slr before so i'm not very good at using it, i take really good phoos in the day, but when it goes dark. My photos turn out rubbish and look like i've used a cheap camera. How do i get them nice and clear and professional looking?

Start reading and learning
kenrockwell.com

Are you using a tripod to hold the camera during the long exposures necessary when shooting in low light?

Are you using the highest ISO settings on your camera and getting the resulting noise in the dark areas?

All you have to do is learn how to use your camera under different conditions to avoid these problems which exist no matter what advanced camera you use.

Here is how to balance the ISO, shutter speed and lens aperture to get the best exposures.

http://camerasim.com/camera-simulator.html

Learn about PHOTOGRAPHY! Learn to use YOUR CAMERA! Good pictures do not happen AUTOMAGICALLY!

You need to remember, while the D3100 is a nice camera it is not built to handle the lower light situations like the professional bodies can. A lot of people refer to ANY DSLR as a "professional" camera, when in actuality the "professional grade" cameras have better sensors and image processing units to handle the low light situations (especially the higher ISO).

The others are correct is suggesting using a tripod and attending a camera/photography course.

The other thing to consider is adding a hot shoe flash and getting better lenses. There are better lenses available than the one that came with your camera (for example a f/1.4 aperture would allow 16 times more light than a f/5.6, and a f/2.8 would allow 4 times as much).

Obviously you're one of those lazy people who expect everything to be done for you… Like having a camera do everything you ask. A rude awakening, welcome to the real world, it doesn't work that way.

Learn photography if you're not to lazy.

Having an expensive camera isn't the magic pill to great photos. You still have to learn how to use it. Figuring out what is shutter speed, aperture, and iso and how to use the camera in P, A, S, and M modes is a great start on how to use your camera. There are plenty of guides online, and always refer to your manual when you need to find how to change those settings. In low light without a tripod, you'll want a high iso setting and a low f/stop value to maintain shutter speeds that aren't too slow.