Question: How can I take photos in relatively dark places like disco clubs and still get a nice background and a sharp subject?
Answer: The key is relatively long exposure, medium ISO rate, and a flash to freeze subject motion. Here's a short explanation: In the club we have typically a dark surrounding, with only the DJ lights or some extra peripheral dimmed lights in sitting areas. You want to emphasize those lights to bring in color and motion to your photos. For that, use ISO rates of 800-1600 (depending on the camera type, and amount of light), and an exposure time (=shutter speed) of around 1/30 - 1/4 seconds, again depending on the amount of ambient light. Also, turn on your flash so it can light your subject and freeze motion. If you're using a simple point and shoot camera you may have a Night-shot Portrait mode that combines long exposure and flash which you can use for that task.