Patience. Asking questions before one makes a judgment as I said before. If one is not clear about something to be more interested in asking a question so we become clear about it. Mindfulness is quite important in Right Listening. Often this has to be done over some time. In the beginning days I found if I was too quick to think I knew, I made more mistakes. So, learning how to give ourselves time to respond to someone I found was compassionate to myself and I'd make less mistakes.
Compassion helps greatly, the wish not to cause harm to oneself and others. Learning how to identify with what a person is saying so that we can see more clearly what's below what they are saying.
Humility helps. Balanced with Confidence. To not think that we know everything or jump to conclusions about what they are saying thinking we've heard it before because it may not be what they're trying to say. One needs patience and compassion to look beyond our first impressions.
Wisdom also helps. If we have some wisdom about the Four Noble Truths, then we may see deeper into what a person is saying. So, as we develop more practical application of the Four Noble Truths in our own life, we are often asking ourselves, "What is the true cause of this?" Then when we see Dukkha arising for someone else, we can consider, what is the cause of it and what do I know about that? And if you don't know about it, ask them, "Can you explain that more?" But often it's the humility to be honest and say, "Oh, I have to think a little bit more about that. Perhaps I need a bit more information before I can make a judgment on that."