Trust and respect all starts from ground work with your horse. Build a solid foundation of respect and trust in the round pen by making them turn in to you when changing directions, do not let them turn to the outside with their rear end facing you, that is VERY disrespectful. Once you have this mastered with your horse, lunge them until you see them keeping their inside ear pointed to you like they're listening, they will then start to lick or chew. They will eventually lower their head, when it is extremely low, as if they're sniffing the ground, drop the lunge whip and face your back to them - this is called joining up. Do not make a sound and do not move towards the horse, keep a relaxed stance. You must have patience and wait for the horse to come to you. Once they do, you have gained a lot of respect and have shown them that you will trust them with it. In my opinion that is the biggest step in the right direction with a new or challenging horse.