Pay attention to non-verbal cues.
This is essential when it comes to effective communication. So much of what we say is actually not said, and if you want to understand what others are really thinking or saying you have to do more than just listen. You have to look and experience too. It's very easy to say something and not really feel it so it's very important that, when communicating, you look both at your own non-verbal cues and those others are sending you. There's a lot to be said for what's not really being said.