I would advise using a tripod if you are doing night shots, and keep the ISO at 100 to keep the image quality high.
You could probably get away with hand held shots, but you'd have to wang the ISO setting up higher to get a faster shutter to prevent blur.
As Kyle said, this will degrade the image with "noise" and the image quality will suffer.
Putting the shutter on a timer will only prevent camera shake if its on a tripod.
If you are just starting out, set the camera to AUTO and let it decide what to do, while you figure out how different settings affect the image.
Alternatively, set the camera mode to aperture priority with an aperture of say f5.6 and let the camera decide the shutter speed.
As I said, use a tripod for best results.
I would shoot raw files as this will allow you to alter the white balance later on in post processing.
This would be useful for correcting any colour cast caused by street or supermarket floodlighting.
If you shoot jpeg, any post processing will degrade the image.
Good luck...don't forget to post your results up here