We know how powerful talking can be at lifting our mood. Here are three qualities associated with people who are especially good to talk with.
Are they non-judgmental? Some people just can't resist sitting in judgment on what you say. You are right or wrong. They agree or disagree with you. Sometimes, they express their criticisms explicitly, other times by giving unwanted advice, often starting with 'If I were you, I'd ...' People who are non-judgmental make good conversational partners.
Do they share? We all know people who'll happily listen to what we say but rarely share the details of their own life in return. They may be good listeners as such but it's a one-way street. This sort of one-sided conversation may be satisfactory while you 'unload' but ultimately it's like talking to a tape recorder rather than a human being. It's good to share.
Do they challenge you? For a conversation to have therapeutic value, your partner must feel free to challenge you when you say something that deserves to be reality-checked. For example, if there's a discrepancy between what you say you believe in and how you behave in practice, then they should point this out to you and you should respond with honesty and openness. Remember, change comes from challenge.