I think that the different skills within communication reside in the basic idea of having to recognize that a simple concept exists in many different forms. Communication involves "the sharing or exchange of thought by oral, written, or nonverbal means." In this definition, exists a skill within the practice. Skilled communication involves being able to convey thought in different forms. Possessing the ability to communicate in different arenas is a skill intrinsic to communication.
Part of this resides in understanding the audience within communication. This understanding of audience is another form of communication. Skilled communicators can target their message and thoughts to a particular audience and have the confidence that their point is understood by the audience. This is a needed skill in communication because if the audience is not able to grasp or understand the message being emphasized, then the entire point of communication is lost or distorted.
Finally, another skill in communication is understanding past experience. This is difficult because human beings are limited in being able to fully understand the experiences of another. Yet, skilled communication involves the ability to, in a limited sense, acknowledging and integrating these realities. It becomes a skill to recognize the individual's past in the process of communication. This is where I think the skills in communication determine success in the idea of conveying thought to another.