Originally Posted by Baraka_Guru

If you go into iTunes, each of the files will have an option to change the volume.

Under "Get Info" and the tab "Options," it's called "Volume Adjustment." It's a sliding scale of +/- 100%. By default it's set at "None." But if you have a file that is louder than others or, in your case, too quiet, you can adjust it here. Be sure to update/sync your iPod after you've made these changes. The files will have to be retransferred.