When gain staging, prior to working on the final mix, I find it very helpful to use this large RMS + Peak loudness meter called rmsPlus.
Sure, my DAW of choice has volume meters on each track and on the master track, but I just find this particular one, very easy to read and more helpful to me than the built in ones.
I set the PK Hold (peak hold) to 3s and that easily enables me to set the peak volume for each track prior to any adjustments of the volume faders.
Click here to download rmsPlus from a Russian web site (scroll down a little).
[ EDIT (Mar 31, 2017): The above link isn’t working but the page and the download are still available via the “wayback machine” by clicking here ]
I haven’t found this hosted anywhere else. I’ve been using this plugin for a while now (on every tune on my web site actually) with no problems of any kind. If my memory is correct, to install it, you just have to place the rmsPlus.dll file where your DAW looks for plugins.