How to earn trust truly depends on the horse/pony. But here's some basic information.
To have trust, you must first of all know your horses attitude nearly better than your own. Now I'm talking about TRUE trust here. You can do anything with that.
Don't yank your horses mouth or be mad. The main key to trust is patience basically. Move quietly around your horse talk to it. This will take a long time. Trust is harder to earn from some horses more than others. One day, if your truly love your horse. You will be able to do what I do on Savannah now.
Me riding Savannah bareback with one lead rope.