It is quite simple indeed (pun intended). "It is better to give than receive." Give to them all that you can and then give them some more. The product of this venture will be significant trust. This applies to all endeavors where one wishes to yield trust.
Establish a positive rapport which illustrates how much you're alike. People tend to be more trusting of those who make them feel relaxed and have a lot of beliefs in common. It helps to demonstrate honesty and integrity by doing what you say you will do over time.
Always mean what you say, say what you mean, do what you say you will, keep promises or don't make them if you don't think you can keep it, never lie, be truthful at no expense, and always come through when needed.