All you need to do is start the conversation. By being understanding, tactful and gentle, there’s a better chance that someone will want to talk.
Some useful phrases: "Are you ok?", "Is there anything you want to talk about?", "Is there anything I can do?", "Why don’t we have a coffee and talk about it?", "I’ve been a bit worried about you.", "I’d really like to help."
Avoid responses which reject their perspective, lessen how they feel, or try to change their view of the situation.
Examples of what NOT to say
These reactions may make the person feel misunderstood and more isolated than ever.
Nobody expects you to have all the answers but that doesn’t mean you’re not helping. You can do good just by being an active listener.