My method for deleting duplicate songs in iTunes, is to click Show Duplicates in my library, create Size and Bit Rate columns and sort by Size. Songs with the same song length will appear next to each other in order. Unless there is something that makes the one with inferior bit rate (such as 128kbps rather than 192kbps) worth keeping, I delete it.
However, if there are a lot of songs with the same song length say 2:41, then the identical song titles could be spaced apart within that grouping. Hence the second method I apply sometimes – same as above except sorted by song Name. Songs with the same name will appear side by side, then I look to bit rate to see which is better (but I listen as well since there are other factors in ripping quality). I also consider the song length as there may be an extra 5 seconds at the start or end of a song, or radio edit with a 30 second difference that I may want to keep.
I like to have songs marked with (live) in the name for live performances, but if it’s not there there yet then you might delete the song by accident. Watch for “Live” in the album (or set a filter for this), or look for big differences in song lengths or years.
Note you can create a smart playlist of songs with “live” in the album title and exlcude this from the list that you apply Show Duplicates to. Similarly, for duplicate removal or just organising purposes, you can create a playlist of songs with “acoustic” in the Name, Album or Genre.
Instead of following the menu dialogues each time for Remove or Cancel, followed by delete or keep orignal, I rather set Name of a song to delete, or Artist to delete for a selection.
This is also helpful because if I apply Show Duplicates to a plain or smart playlist, I can’t delete the song off my disk from there. So I mark it as delete, then later in my library I find a whole lot matching that word and remove them from iTunes and the disk.