Think about how you feel yourself when someone says he or she is listening to you, but then also is paging through a report or checking the clock or giving other non-verbal signals of little or no interest in what you have to say. A mistake that poor listeners often make is inserting their own experiences in a way that minimizes what the talker has to say. A friend may tell you that they are upset because he just scratched his new car. Such a response says to your friend that his experiences really aren't important, only yours. And that is not a path to real friendship.
Confidentiality is also important.
Not keeping private information private is a quick and sure way to destroy a friend relationship. In dealing with private information, it is important to define your limits when a friend is sharing with you. If someone is giving you information that makes you uncomfortable, explain what knowing that information is doing to you. At times, it may be necessary to define the limits of what you are willing to listen to or talk about. Communication is a vital part of a good friendship.