Professional Courtesy
Professional courtesy is one of the most important skills that every individual should have. Some people may think that their project experience and resume are good enough for everyone to want to use their services. These people are wrong. You can have the most impressive resume in the world, and work on some of the biggest projects in the United States. However, if you do not act in a professional manner, all of your experience means nothing.
People do not want to do business with people who they are forced to chase down to get answers, or get a timely response. Even if you do not have an answer, it always helps to give a call and just give a status update. Let the person know that you are working on their project/reviewing their proposal/preparing response to their evaluation etc. That one minute phone call will go a long way in maintaining that positive opinion of the person you are dealing with.
Remember, all you need is one rotten apple for the others to start going bad.