When syncing iphone 5, itunes hangs on backup stage
Delete any old backup related to this device


Open finder
command-shift-g to open the go to folder.  Put in ~/Library  Hit go
Navigate to Application Support > MobileSync > Backup
Order by Date Modified and look for the latest folder which should be timed at the last time you did a backup.  Drag the folder out to the desktop
Try to resync with the phone


If it all works you'll get a new backup in the folder, delete the one on your desktop.