Here’s a quick tip about how to find a good chunk of old data to delete, to give yourself some extra free space on your Mac. If you’ve ever upgraded iPhones (or iPods or iPads), you might have old, unnecessary backups hidden on your computer, taking up a lot of space. You can check by following these steps:
Open iTunes
Go to the iTunes menu (top left, in the menu bar)
Select Preferences
Go to the Devices tab
In there, you’ll see a list of device backups, and the date they were last backed up.
To remove one, click on it, and then click the “Delete Backup” button.
Be very careful when you do this, make sure you don’t delete the backups of your current devices (or any old backups that you haven’t restored to other devices). Note that the backups are sorted alphabetically by device name, not by date of last backup, which can be confusing.
In my case, I was able to clear out 23 GB of old, useless data
RT 
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