Motorola Media Link and music sync

[SUPERSPORT25]

Ok so I use MML to sync my music to my phone but kept noticing duplicates each time it syncs. For example some of my songs are tripled of the same song, even albums. I have all my music in a folder on my laptop. My question is lets say you transfer 800 songs the first time. Then you add more music to your library. I do not want it to duplicate so what is the best way or program to sync without duplicating into the phone?????