Try these tips.
About “Other”:
http://support.apple.com/en-us/HT202867
Go step by step and check.
1. Start up in Safe Mode.
http://support.apple.com/kb/PH11212
2. Backup your computer.
3. Empty Trash.
Finder
Click on an empty spot on the Desktop to activate Finder.
Right click on the Trash icon in the Dock.
Click “Empty Trash” to empty Trash.
Mail
Click Mailbox in the in the Mail menu bar.
Erase Deleted Items > In All Accounts
Erase Junk Mail
Photos
File > Recently Deleted > Click the “Delete All” button at the top right corner
iPhoto
iPhoto > Empty iPhoto Trash
https://support.apple.com/kb/PH13806?locale=en_US
4. Disk space / Time Machine / Local Snapshots
Local backups
http://support.apple.com/kb/ht4878
5. Delete old iOS Devices Backup.
iTunes > Preferences > Devices
Highlight the old Backups , press “Delete Backup” and then “OK”.
http://support.apple.com/kb/HT4946?viewlocale=en_US&locale=en_US
6. Re-index Macintosh HD.
Storage categories shown are based on Spotlight index.
This will take a while. Wait until it is finished.
System Preferences > Spotlight > Privacy
http://support.apple.com/kb/ht2409
7.Try OmniDiskSweeper. This will show the storage size details of the items.
https://www.omnigroup.com/more
Select Macintosh HD and click “Sweep Selected Drive” at the bottom.
Be careful. Delete only the files that can be safely deleted. If you are not sure about any file, don’t touch it.
8. Move iTunes, iPhoto and iMovie media folders to an external drive.
iTunes
http://support.apple.com/en-us/HT201562
iPhoto
http://support.apple.com/kb/PH2506
iMovie
http://support.apple.com/kb/ph2289
