What does communication have to do with success? To start off with, poor communication causes a loss of productivity, reduced quality of life, and stress. The way you communicate with another causes a lasting impression, good or bad. If you communicate effectively with another person you may have found a lifelong client, friend, or colleague.
"Communication leads to community, that is, to understand, intimacy, and mutual valuing." - Rollo May

1. Learn to listen! - One of the biggest reasons people do not communicate effectively is because they do not listen. Instead of planning ahead and thinking of something to say, listen to what the other person is saying-this will let you know what your response should be! What are some other good tips for being an effective listener? Try to reduce the distractions and interruptions around you, Show interest in what the person is saying by making eye contact, Confirm what you have heard by restating the main point, Listen for the feelings behind the message and not just verbal communication. Be sure to ask open-ended questions to keep the conversation flowing. 
2. "Think before you speak." - Yes, you have heard this since you were very wrong but how often do you practice it? Be sure to listen to what you are saying before it is spoken to ensure it is exactly what you want to say. Do people often misinterpret what you're trying to say? Then take a moment to make sure what you are about to say sounds like what you are meaning to say. This will also help you to sound more confident because it limits hesitation as you've already practiced saying it in your head. This will ensure to the listener you mean what you say and you know what you are talking about!
3. Body Language- Body Language is a great way to help get your point across. According to the Total Communicator, more than half of your impact as a speaker depends upon your body language. This includes your gesture, stance, and facial expressions. Make sure to use your hands to emphasis your points! Body language can also halt your attempts to communicate-leave out eye rolling and sighs. Although it may seem silly at first, stand in front of a mirror and act like you are having a conversation with a client. Evaluate yourself on what you may seem like from an outsider.
4. Be Respectful- Even if you don't agree with another person's point of view, be respectful. Keep as calm as you can and do not resort to swearing, raising your voice, or put downs. Clearly and peacefully state your point of view. If you can tell it is a sensitive issue for either you or the other person, smoothly change the subject.
When you learn to effectively communicate, connections are easily made, and the opportunities are limitless.
Thanks. Bookmarked. You should add more thing though: respond in a timely manner. I got annoyed when people do not respond promptly or no response at all.