Hi

You don't really want your audio hitting the red area in the volume meter (which is measured as 0DB I think) as this indicates frequency clipping and possible distortion. If you already have your clips in the time line your best bet is to select the clip and then from the dropdown menus choose Clip>Audio Options>Audio Gain. Click the normalize button inside the dialogue box to find the highest possible volume without any clipping or distortion (in other words keeping the volume meter outside the red). This will give you a pretty good start for a good-quality, uniform volume throughout your video.

Hope this helps

Matt