Nobody does, they are officiated differently by each crew, conference, and even game to game.
I did not think today's should have been a target just based on ball was tipped the safety had his head up and did not launch or lead with the crown of his helmet. I would not have been surprised if it was called because nobody really knows what exactly targeting is. To me there needs to be some kind of intent like the launch or crown and there wasn't there.
Would Jeremiah Smith already be a top 10 WR in the NFL?