Nikon D300s what settings?

Hi i've got a nikon d300s and my son's friend has asked me to take some pictures of a party in a nightclub for him the lighting is going to be on the darkside so can anyone advise me of how to set the camera up ie shooting mode S, A, P or A also what f stop and the shutter speed, ISO ect. As you can tell i'm a novice i do have some idea but would like a bit of guidance as its his 21st party and don't want to come away with pics that are useless

3 ways to get more light onto your sensor:
1. Use the widest aperture your lens is capable of.
2. Slower shutter speed
3. Higher ISO.

You will also want to adjust the white balance to the type of lighting that is present, or the colors will be all wrong.

I can't predict what the conditions will be, and also don't know what lens you have, so you will have to play around with it to get it right.

Start with wide open aperture in aperture priority and see what happens with iso at 1600 letting the camera choose the shutter speed. If it's blurry, you need to up the iso. You will get more noise with higher iso, so use the lowest you can. Once everything looks good, start experimenting with lower iso, & stopping down aperture. You will always get better results when you aren't pushing it to the limit.

If you have a kit lens, just remember, as you zoom, the aperture changes (gets smaller), so you will have to adjust for that. Shooting in the dark is not easy, especially with slow lenses. You may need to use a tripod to avoid blur if you do not have a VR lens. Use an external flash if possible. The built in may be good for close ups, but will get lost in a large environment like a night club for distance shots.

Use flash with a diffuser.
Shoot either in Shutter speed priority or manual with the shutter speed set to 1/250th second (the flash sync speed of the D300/D300s)
Practice long before the event so you have a good handle on what you are doing

A mode with flash on.

Why do you have a Nikon D300s if you can't use it?
You seem to have all of the gear and no idea.