Here's some older references I have:
Have a look at how space is being used:
OmniDiskSweeper (ODS) (free) - http://www.omnigroup.com/applications/omnidisksweeper/download/
2012 Linc Davis tips on running ODS as root user so it sees all files - https://discussions.apple.com/message/19336100 In Terminal:
"Don't delete anything while running ODS as root. When you're done with it, quit it and also quit Terminal."
OS X Lion: About Time Machine's "local snapshots" on portable Macs - http://support.apple.com/kb/HT4878 - “You may notice a difference in available space statistics between Disk Utility, Finder, and Get Info inspectors. This is expected and can be safely ignored. The Finder displays the available space on the disk without accounting for the local snapshots, because local snapshots will surrender their disk space if needed." "To clarify, none of the 'Other' category represents local snapshots." - https://discussions.apple.com/message/18990711
Hidden local backups with Mac OS X Lion filling up your MacBook hard disk! - http://blog.valerio.de/post/19238158977/hidden-local-backups-with-mac-os-x-lion- filling-up-your - Time Machine using local drive to store backups when external drive is not available.