When someone tells you they'll get back to you on something and they do, that's a sign of keeping one's word.
When you offer someone something and they actually respond one way or the other, that's a sign of acknowledging your initiative.
When someone opens up to you (sometimes somewhat randomly), that's a sign that they trust you and are comfortable enough (and ready!) to share with you.
In these instances and many others, we can learn so much about the people in our lives and fully appreciate them for who they are and what they mean to us. Maybe you won't be the person who they spend the most time with or even talk to that often, but you'll be the person they go to when they feeling low, and in most cases, that means so much more.