In sound forge there's a tool called "Normalize" It comes pre-set for music at 16, but I know bands are setting it at 6. 10 is pushing it. The good thing is, when you're working with a sound file, you can test it and not destroy your original file.

If you analyze the "hot" tunes - there is actual, true 'clipping' - parts of the sound clipped off. But, it can't be heard by the human ear anyway. Mostly I see this in punk files, but the past few years it's happening in pop, etc - to give the listener an immediate "punch".

For example, they just took out one of their regular CDs that they've been listening to for 10 years. This 'punch' makes the song sound brighter. The volume is simply higher on the cut.

Scott said it - we're all divided on the usefulness. If your song sounds great loud, then I really don't see why not. If it sounds distorted, etc, then DON'T do it. As Jody implied, it's what equipment you have available that will allow you to punch it.

You can re-master your demos if it's something you really want to do.