The world runs with a rule that causes make the results. If you want to take, first, you need to give.
Trust is also the same, if you want to be trusted, first you need to be a trustworthy person, by being honest and sincere. Be honest in what you do so others can trust you. Be honest with yourself so you can believe in yourself.
On the other aspect, sincerity is the feeling accompanies words and actions. Other people can know if you are honest or not or they can sense how much sincere you put in by watching your actions and hear your sayings. Sincerity will connect your feelings to those of the others.
When you are honest, you convince the minds of others. When you are sincere, you conquer their hearts.
Therefore, be an honest and sincere person, you will become a reliable person, and people will trust you.