OS X 10. 7 Lion / 10.8 Mountain Lion / 10.9 Mavericks
Try these tips. Go step by step and test.
1. Start up in Safe Mode.
2. Empty Trash.
3. Delete "Recovered Messages", if any.
Hold the option key down and click "Go" menu in the Finder menu bar.
Select "Library" from the dropdown.
Library > Mail > V2 > Mailboxes
Delete "Recovered Messages", if any.
Empty Trash. Restart.
4. Repair Disk
Steps 1 through 7
5. Disk space / Time Machine ?/ Local Snapshots
6. Delete old iOS Devices Backup.
iTunes > Preferences > Devices
Highlight the old Backups , press “Delete Backup” and then “OK”.
7. Re-index Macintosh HD
System Preferences > Spotlight > Privacy
8. For more on this and very helpful tips:
Freeing Up Space on The Hard Drive
2. You can remove data from your Home folder except for the /Home/Library/ folder.
3. Visit The XLab FAQs and read the FAQ on freeing up space on your hard drive.
4. Also see Freeing space on your Mac OS X startup disk.
5. See Where did my Disk Space go?.
6. See The Storage Display.
You must Empty the Trash in order to recover the space they occupied on the hard drive.
You should consider replacing the drive with a larger one. Check out OWC for drives, tutorials, and toolkits.