This seems like a given, but so few people try anymore.
It seems people have lost the skill of listening in this crazy world we live in. It always shows someone how much you care about them when you remember something that they told you. Such as "How was your trip to (specific location)". When you are having a conversation with someone respond to what they say. I had a teacher once who when he said hello to you (besides the fact that he also knew the name of every student in the 1,300 + student body) he remembered something you had told him. He cheered up a lot of down teenagers by just listening to them.
