Have your head down, eyes downcast, shoulders slumped, and slowly open the gate. Extend your hand for him to sniff. Slowly and politely put the lead around his neck and bring him out of his stall. You don't need to pet him or talk to him. Just be quiet.
If he turns his back to you while you are at, or going into, his stall - don't go in because it's a huge sign of disrespect. and he is telling you he doesn't want you there. Pay attention to his attitude and listen to him.
Get him to turn toward you, stay quiet, then, once he is facing you, approach him.
To get him to turn toward you, lightly throw your lead rope or a pebble, or whatever, toward his ass end (obviously while you are a distance away), or whatever it takes to get him to move so that he faces you and you can stay safe.
As many of the top clinicians say: "Better two eyes than two heels".
Mostly we just barge into the stall and grab the horse and drag him out of there. It's impolite and disrespectful. Your horses' stall is his home where he feels safe and secure and territorial.- just like you do in your own home or bedroom.
You don't want someone just walking in on you. Well , neither does your little darling. He'll appreciate your courtesy.
Mary Dixon Adventure Horse Riding in NYS RideNYS.com