low light - What should my plan be for photographing in a nightclub setting?

I'm going to be photographing in a club setting. Imagine a foggy atmosphere, with a lighting nightmare: everything from strobe lights to colored spotlights and everything in between, both bright and dark. The atmosphere is very fast-paced.

I'm looking for tips on lenses, ISO settings, camera settings (I have a Nikon D90 if that helps), since this is such a difficult atmosphere, I want to go in at least having some sort of plan.

Answer

It's at times like this that digital photography really out-shines anything you could ever do with film... because you're going to get a lot of missed shots.

Here's a strategy that's worked for me in the past: Get an external flash with TTL (very important) and an off camera cable. A mid-ranged zoom will be fine, it doesn't even have to be a good one, you're going to be shooting at f/5.6 or f/8 anyway. Don't use a 50mm on your D90, it's going to be too long. If you can get a flash bracket, that'd be even better. I know it looks a bit ridiculous, but putting the light off the camera is a god-send quality wise AND it will signal to the club goers that you are a serious photographer, not just some creep with a camera. That actually does make a big difference in how they react to you.

To start shooting, set your camera to Manual mode, What you want to do is to get up close with your subject, but keep the in the night club context. You don't need high ISO to do this, 400 will be more than enough. Drag the shutter a bit, 1/30 or 1/15 and keep your aperture around f/5.6-f/8, that should be more than enough with a crop sensor. This will let you freeze your subject (speedlites shoot at up to 1/10000s) while getting enough ambient light to keep them in a club setting. I'd stay on the wide-end of your focal range, that puts the viewer "in the middle of things", using longer focal lengths makes them feel like they're looking at something happening far away.

Resist chimping after getting the first few shots, spend time in the club shooting, you'll get a chance to check it all later. Shoot extra, you never know if someone shut their eyes. Just get in, pop pop pop, get out. Bring extra batteries. You might not be able to AF because the club might be just too dark, but if you shoot people from more or less the same distance at f/8 you probably won't need to.

Cool effects I've seen used: wide angles (10-22) with the flash set to a longer distance, that lights just the middle of the frame while creating a cool fall-off around it. Multiple exposures to tell a story in a single frame.

Oh, and do what Michael Bolli said - test it out on your friends at home first, but to be honest it's a pretty easy for of photography to get right. Concentrate on getting interesting looking people and situations over the technique tho, because nobody's going to care if a shot isn't perfectly lit as long as the content is great.