the best thing is to listen and don't pressure yourself to fix it (the situation), just be there and support them through it. I often find that most people just want to be heard, so even if you don't know what to say just the fact that you're there listening and caring helps them feel better. You could try saying things like "I'm here for you" or "I'm sorry you're going through this" to let them know you're there. It doesn't have to be perfect, just genuine. :]