Here are a few tips and techniques on how to get rid of duplicate songs in your iTunes Library as well as some precautions you should take before deleting duplicate tracks.
How To Remove Duplicate Media From iTunes
As your iTunes Library grows, you will probably lose track of exactly what media you have already imported. Eventually you will end up with duplicate songs and videos. For example, you might accidentally import a CD twice or add files from Limewire or BitTorrent. Or maybe a friend with a big Terabyte hard drive loaded you up with a lot of music recently.