The so-called 'photo button trick' can help you get the exposure right, when you film in low light situations / total darkness. The tutorial was made for the Canon HV20 but works for the HG10 as well (they share menu / software).
The footage happens to be me filming the tutorial :). You'll see my HG10 filming with no gain (at the lowest ISO setting possible for the camcorder). The footage used on the screen in the video is the original tutorial from The DV Show. It seems confusing at first, but by the end you'll see he's recording a computer monitor with the video on it.