In analog days, there were standard audio levels, but with digital it's not so much a standard as a personal preference. I usually normalize the entire audio track then reduce to 50%, that's 6dB down from max and isn't likely to startle the viewer. Then if I need to, I'll go back and custom set levels on extra loud or soft sections.
Modern Pop/Rock music tends to be fairly high level all the way through, so setting to 70% is ok. But if the mood is low key ambient 10% may be better.
Fav quote - "Experience is whatcha don't get 'till ya don't need it no more."
System - Athlon 1.4GHz, Win98, Hauppauge PVR250 receiver and compressor.
Software -Magix Movie Edit Pro 10, Nero 6 + NeroVision Express, Moho 4.61, PSP 8.1, Bryce, Quicktime 6.52 pro, Goldwave 5, DVD-Lab.
Cameras - Panasonic GS9, Canon ES8400V, Canon EOS D20 and Canon A70