This photo was shot with ISO 200 and and an exposure time of 30 seconds. Of course I switched on the "noise reduction option for long exposure" option of my Nikon D700. Since I had no tripod I used some non-professional stuff like my purse to fix the camera at the ground.
It was even accepted for assignment.
If you want to make good night photos you should invest in good equipment.
It depends on the quality of your camera (a low quality camera will give a lot of noise and you can't do almost anything to solve it), the ISO (try to use the lowest number you can) and try using a program like Photshop, Lightroom or Corel Paint Shop Photo to reduce the noise...
without seeing an example and the EXIF info, all i can suggest is that the usual cause would be using too high an ISO setting or an extremely long time exposure. Are you trying to handhold or using a tripod ? Are you using in-camera noise reduction for long exposures ? (if your camera has it?-I assume it would, check the manual). Try getting a faster lens, such as a 35 or 50mm f1.8, and using a tripod, which should let you use a reasonably low ISO at a reasonably short exposure. And if all else fails, try noise reduction software such as "Noise Ninja" (http://www.picturecode.com/) or Topaz deNoise.