depending on what genre of music your doing the so called standard could change .. I would say your mix should have a reading of around +4db ... check out this link , they make a very very good plugin for this http://www.elementalaudio.com/products/inspectorxl/
Try it out using FlexiMusic Wave Editor, an audio editing and converting software. Play the audio files in this software, from the menu; select “volume†command where in either choose simple Compress/ Expand or Dynamic Compress/ Expand option to equalize the volume throughout the whole audio file. It is best to opt Simple Compress/ Expand option. The usage of Simple Compress/ Expand option is that, it will choose the optimum (maximum) level of volume of the audio file and this will be applied for the whole audio file. While using Dynamic Compress/ Expand option, the volume will be changed randomly. This option will increase the volume where it is low and decrease the volume where it is high.http://www.fleximusic.com/waveditor/overview.htm