Step one: let him hide or shy away from you if he wants to. He wouldn’t let me touch him for a couple days after we got back from the shelter. His comfort was more important than me getting to touch him.
Step two: make yourself nonthreatening. In my case this meant being very quiet, bringing food and lying down on the ground within his eyesight as an invitation to investigate.
Step three: watch his body language and don’t do things that make him uncomfortable. Turns out my cat often bit when he was overstimulated so I made sure not to overwhelm him.
Step four: draw lines, but not with brute force. Even though his biting wasn’t meant to hurt, I wanted to make sure he wouldn’t injure anyone in the future. So I decided when he bit me, I’d yelp “ow!” And then withdraw all physical contact for a few minutes, sometimes leaving the room. Now he never bites, but sometimes he puts his teeth on my hand and then thinks better of it.
Step five: provide a good outlet for destructive behaviors. Aka PLAY WITH HIM, SEVERAL TIMES A DAY.
Step six: be patient.
Step seven: get lucky and somehow pick up the best cat in the entire shelter. I don’t know how it happened but he’s a godsend. He’s literally cuddled me out of a panic attack. We both really needed each other.