Originally Posted by mrchattr
I have never worked with Audacity, but here's something I used to do all the time in this situation. I used to record on a Korg D-16 digital recorder. One thing you can do on that recorder is copy tracks, start to finish. If someone recorded something that was a little too quiet, and the usual turning up, etc, didn't work, I would copy the track a few times, onto different tracks. Suddenly, you have two, three, four, or more of the tracks to work with. Then, if you change the panning of the track just slightly, it will have the effect of increasing the volume (at least, that's what it sounds like to the ear...you are basically tricking the ear). This always worked perfectly, though it was a bit time-consuming.
If it's a digital recorder, that'll have the same effect as turning up the gain, if it's sample accurate.
The answer here is compression. Make sure the tracks are normalised, then put a compressor (or even better, a limiter) on that track to reduce the transients so that you can increase the gain. This is what makes commercial recordings so 'loud', the increase of the average sound level gives the impression of greater loudness at any volume, even though the level never at any point exceeds 0dB.