- Tell the truth.
- Be sincere. Say what you mean and mean what you say. ...
- Keep your word.
- Be reliable.
- Return things you borrow.
- Keep private information private.
- Don't gossip.
- Don't ask a friend to do something wrong to keep your friendship.
David Wolfe has said that the four traits of a trustworthy person are:
- They are their true selves. They're not leading their lives under false pretenses. They are who they are and that's who they are. The good, the bad and the ugly. They're not afraid of who they are and don't lead on they're more than they're cracked up to be.
- They always keep their promises. Talk is cheap. Keeping the talk you utter is priceless.
- They do the right thing. It's not always the popular or easy path to take -- doing the right or the easy thing... but knowing it'll be weighing on your consciousness outweighs the need to bend to be part of the sheeple.
- They never make you feel inferior.
Check out what else he has to say about these traits here.