Recording Sound: Levels
When you're recording digital sound, adjust the input volume as loud as possible without distorting.
On the VU meter, never let it get over 0. Zero and over is usually red--keep it just under the red.
VU meter examples (you don't have to copy this part):
Analog meter example (too quiet--should peak at -2 or -1, which is in the black just under the red). This is a really long video; just watch it for 15 seconds or so and you'll get the idea.
Here's one that looks properly adjusted until the very last few frames of the video (it peaks into the red then).