Originally Posted by GYAVAN
For the private game, here is a little tip.
Create your private game then invite your friend(s) but don't press A for the moment. Wait for your friends, let them choose and confirm their character and then, you press A and quickly select yours. No one else will join your game that way.
Sorry but that guarantees nothing. We had strangers join in while the invite was being sent and accepted sadly. until until the private lobby bug is patched there is no way to ensure that random people don't join your game.