Here is a really cool feature in iTunes that is often overlooked: “Show Duplicates”. This is especially good for people that download music from multiple sources and don’t take the time to check each song that will be downloaded. (I’m guilty of this!)
To have iTunes display a list of all duplicates, go to VIEW > SHOW DUPLICATES. You can then choose what to do with them. You can press SHIFT and CLICK to select songs in consecutive order or you can press COMMAND (APPLE) and CLICK to select songs not in a random order. Then hit DELETE. iTunes will then ask you to move files to the trash or keep them at your iTunes folder. You can decide what to do.
Have fun organizing your music!