Thanks to another user, I’ve now learned how you can turn of Resume completely. This is not the same as stopping Safari from starting up by opening your previous tabs. For that, use the commands I gave you above.
However, it will stop Safari, and anything else, from starting up when you reboot – what I love about this hack is it you don’t even need to uncheck the box in the Login window!
All you do is this:
1. Close all windows and quit all apps.
2. In Finder, hold down the Option key and click ‚Go‘ in the menu bar at the top.
3. Choose ‚Library‘ (you have to have the Option key held down to see Library in the menu).
4. Navigate to Library > Preferences > ByHost > com.apple.loginwindow.[xxxxxxxxx].plist
The [xxxxxxxx] represent some interminable string of numbers and letters. What you need to check is that its ‚loginwindow‘ and ‚.plist‘ at the end (don’t make the same mistake as I did and choose the Unix exectuable file).
5. When you’re sure you’ve identified the right file, select it and press Cmd-i to show the ‚Get Info‘ window. Click the ‚Locked‘ option.
6. Now, test that it works. Close the ‚Get info‘ window and the finder window. Open up Safari, Preview and a couple of windows. Do a restart and behold – a clean desktop!