Settings on dslr camera?

This weekend i'm seeing a show in a dark theatre that doesn't allow flash photography.
what setting should i put my camera (nikon d300) in?

I would set the aperture at max, then play with the shutter speed and ISO to see what gets the best results. You will have a challenge, no doubt.

put it on manual mode, keep the aperture at it's widest, and ISO at 800 to start out with. Remember to use your light meter. It is your friend. It will not hurt you.