Concert photography low light

I own a Nikon d3100 and am taking photos in a very low light area. What's a good setting to set my camera at? I want to get as still/clear shots as possible.

Use the light meter on the camera with the lens aperture wide open. Adjust the ISO until you can shoot using shutter speeds at 1/250th or faster.

Do you have permission to use a dSLR at the concert? Most prohibit the use of dSLR's in their venues unless the photographer has venue pass and some kind of press credentials. If you had those, you would probably not be asking such a question about relatively easy exposures

Very high ISO and a lens with large aperture

(3, 200)

What kind of lens are you using? Using a tripod might help. If you have say a 50mm f/1.4, or even a 1.8, open up the aperture all the way. Set your ISO as high as it will go, which on the d3100 I think is about 1600, but I may be wrong about that. Also, when you take a light reading, and you are using the light meter in the camera, try not to include the darkness of the audience, as this will effect your reading. What is important is the people on the stage, which is usually relatively well lit. So if you can, walk up to the stage, take your reading of the well lit area, and set your shutter speed. If you aren't using a tripod, anything below 80 or so, you will get blurring. Depending on the concert, I don't think there will be a lot of movement, which will effect the clarity, so if there isn't, you don't have to set the shutter too high, and therefore can maximize the amount of light you get. It's an art finding the right balance, because with the aperture opened all the way up, you will have a very short focus range, meaning anything outside of the point of focus will be blurry anyway.