Would you be open to the idea of using a tripod?
I use a Nikon D40. I can give you very detailed tips if you choose not to use a tripod. My settings are very customized as I favor the P mode...What model Nikon are you using?
For basic, basic suggestions for anyone doing night lights:
No Flash!
Use a Hi ISO setting, 800 - 1600 or even higher.
Line up your shot,
pull your elbows all the way in to your side,
take a breath, hold that breath
and click.
ETA: You can get a good long exposure by using a solid surface like a trash can top to set you camera or elbows on to help steady your hand.
If you are doing night portraits. Use the night setting, you'll need the flash, and have them hold still til the photo is done - you'll get people blurs if they move before the shutter finishes.
Aisling and Brenda, that's only the stuff I've put in PB!
I use an external Sea Disk for the thousands of originals I have in my puter.
I see the world in photographs and have been at it for twenty years.
I don't *know how* to put the darn thing down!