How Do I Take Photos at Dusk and at Night?
Controlling aperture and shutter speed are the keys. Aperture is the size of the lens opening; you want large apertures to let in as much light as possible. Shutter speed will control how long the shutter stays open; the longer it's open, the more light will reach the sensor. Also, setting higher ISO speeds will increase the "light gathering" ability of the camera's sensor.
If you're using a VR (vibration reduction) lens, activate the VR. But if you're using a tripod—which is a great idea for night shots, as it will stabilize the camera during long exposures—be sure VR is turned off. Shutter speeds that are likely to yield the best results: 1/15, 1/8, 1/4 second or longer—and you'll need VR or a tripod for those.
For more advanced night shots, a tripod is necessary. Long exposure times—one, ten, even 30 seconds—combined with small apertures (for great depth-of-field) will produce dramatic light-trails and reveal details.