How do I equalise volume of tracks on itunes as some tracks quieter

iTunes: About Sound Check - http://support.apple.com/kb/HT2425

If you are willing to spend US$30, this program does a good job. http://www.mani.de/en/ivolume/index.html

Highlight the track in iTunes, Get Info, go to the Options tab, move the volume adjustment to suit your desired level.

As a rule, I always crank this up whenever I get any music.