If you own a D700 or 5D Mark II, their miraculous sensors make it incredibly easy to shoot at night without extra gear. But what if you own a $500 DSLR? Photography Bay has some basic reminders for night shooting.
Their tips for shooting with a lower-end DSLR without carrying gear like a tripod can be boiled down to cranking up your camera's ISO—your camera's light sensitivity—but not too much. Like ISO 400 for older entry-level cameras, up to ISO 800 on newer ones like the D90. Then minimizing camera shake using the breathless technique—squeeze the shutter at the moment you've exhaled all the breath in your lungs, kind of like a sniper. It helps even more if you've got your elbows tucked at your sides.
Or you can cheat against not having a tripod by setting your camera down on something so it's immobilized—jackets are good for this—and setting a slightly longer exposure time to let in more light. (A fast lens, say F/2.8 or faster, helps.) There's also this cheap, disposable stabilizer that fits in your pocket. You'll get a cleaner image that way, with a lot more light in cityscapes (like Times Square). Oh, and shooting after it rains is great since the water reflection increases the amount of light flooding into your camera. But above all, you need to know what your camera setup is capable of doing.