More important than speaking
How do you know if you're a good listener?
Even if you think you "listen good," it won't be of much value unless the people you are listening to feel that you listen to them well. Survey at least five diverse people in your life (family, friends, colleagues, bosses, reports, even casual acquaintances). Try to make them feel as safe as possible to answer candidly the following question, "On a scale from 0-10, how would you rank my listening of you? A ranking of 0 means I'm the worst listener you ever met. A ranking of 10 means the I'm the best." If they rank you at less than an 8, ask them a followup question, "Please give me tips as to what I might do more, less, or differently so that your ranking of me would be a 8 or higher?" Thank them for their coaching in helping you to become a better listener.
Patience and Curiosity
You will have problems listening well if you are impatient (just waiting to say what you want to say or to leave the conversation). Impatience is typically caused by not enjoying the process. Use the tools at the NNI toolkit to find ways to enjoy the process of listening. One of those important tools is creating curiosity about hearing and understanding what the other person is trying to communicate.
Reflective listening (and making acknowledgement sounds)
If you're not clear about how to listen reflectively, plenty of quick resources are on the Internet. Reflective listening not only helps ensure that the other person is aware of your attentiveness and curiosity, but also keeps the two of you on the same page. Moreover, making acknowledgement sounds ("okay... got it... tell me more... yes... keep going... ahh...") is helpful to indicate listening. Making these sounds (not too many, though) is more important when talking on the telephone than when face to face.
Set it up so that you're taking care of yourself while you're listening
If you have limited time (or only feel good about listening within a tight time frame), create this understanding with your conversation partner at the beginning. For example, say, "I've only got ten minutes now for this conversation...does that work for you?"
If necessary, when talking with someone who "goes on and on," consider choosing courage to be "rude" and interrupt them in order for you to contribute to the conversation. It probably won't even occur to them as rude.
If you're still having trouble enjoying the dialogue, initiate a Partnership Conversation with the other person to find ways that you can both enjoy the interchange. Start with, "Somehow I'm having trouble really engaging in this conversation with you. Could I ask for your help in figuring out a way that we can both have fun talking together?"
Listening vs. obeying
Most of us grow up conflating listening and obeying (or agreeing). The act of active listening is entirely distinct from either obeying or agreeing. If you haven't clearly made this distinction for yourself, listening well becomes problematic. Know without a doubt that you can listen well (and the person who you are listening to will feel that they were listened to), regardless of whether you obey them or even agree with them.
"Seek First To Understand, Then To Be Understood."
-from Stephen Covey's "The 7 Habits of Highly Effective People"