Start off by being trustworthy in the small things of life. The other person must start trusting you in these small things before they start trusting you with the more important things. For instance, if you cannot reach a destination on time and cannot be trusted with this, how can the other person trust you with other things which you claim you will be able to do?
Always have the other person’s confidence. Make sure that whatever the other person wants you to keep to yourself, remember to keep it to yourself. Don’t let it out. This will help the other person have a little confidence in you. Avoid the everyday gossip to help this person earn confidence in you.
Try sharing your personal information with this person as well. Relationships are always built when both the parties are agreeing to the same thing. If the other person is sharing information regarding him/her, then you should return the favour.
Always opt for things that the other person likes as well. You have to make the other person realize that you are ready to make sacrifices for him/her. Their needs should become your needs too. They should understand that you are there to take care of them whenever they need you. This is where trust comes into play.
Spending time with the other person helps a lot. Try to give your time to this person through phone, text messages, e-mails, letters, and even through one-on-one conversations. Spending time together is absolutely necessary and since we are living in an advanced ear, even if you are not together all the time, you can use other mediums to talk to each other.
In case you see that you have made a mistake, then apologize first. It’s okay to apologize. People often have their egos, but in order to build trust, you must set this ego aside.