To be honest, I'm not the most trusting of people, so I guess the better question would be how does someone earn my trust? The answer is: with difficulty. Agree with me on the important stuff and back me up in arguments with others who are less informed. Prove that you're on my side by backing up your words with action. Be there for me with food and alcohol when I'm feeling like shit. Make me laugh. Catch me when I fall. Most importantly, if I tell you a secret, or you happen upon one, you better damn well keep it.
Trust is one of those things I don't think I can give back to someone once it's lost. It's something I am quite conscious of. I've lost a few friends over the years...
Has anyone ever betrayed you?