What is communication?
John Adair, the world’s leading authority on leadership and leadership development suggests it is: "The giving, receiving or sharing of ideas, knowledge and feelings (the contents of the mind, heart and spirit of man) by such means as speech, writing or signs."

At its heart communication is a two-way process involving a sender and receiver.

The Sender. Who we are influences what is heard and the impact of our message. The role, status and our relationship as givers and receivers is critical.

The Receiver. Who is on the other end of your message? Is it a subordinate, colleague or superior? Is it someone you know well or a stranger? The answer to these questions will influence how much you say and the language that you use.

The communicator Donnell King suggests there are four key principles, which underlie the workings of interpersonal communications, which cannot be ignored:

It is inescapable
We can't not communicate. The very attempt not to communicate communicates something. Through not only words, but through tone of voice and through gesture, posture, and facial expression we constantly communicate to those around us. Through these channels, we receive communication from others. Even when you sleep, you communicate. Remember a basic principle of communication in general: people are not mind readers. Another way to put this is: people judge you by your behaviour, not your intent.

It is irreversible
You can't really take back something once it has been said. The effect must inevitably remain. Despite the instructions from a judge to a jury to 'disregard that last statement the witness made', the lawyer knows that it can't help but make an impression on the jury. A Russian proverb says, 'Once a word goes out of your mouth, you can never swallow it again'.

It is complicated
No form of communication is simple. Because of the number of variables involved, even simple requests are extremely complex. Theorists note that whenever we communicate there are really at least six 'people' involved:
 who you think you are;
 who you think the other person is;
 who you think the other person thinks you are;
 who the other person thinks he/she is;
 who the other person thinks you are; and
 who the other person thinks you think he/she is.

We don't actually swap ideas, we swap symbols that stand for ideas. This also complicates communication. Words (symbols) do not have inherent meaning; we simply use them in certain ways, and no two people use the same word exactly alike.

Osmo Wiio gives us some communication maxims similar to Murphy's law [Osmo Wiio, Wiio's Laws--and Some Others (Espoo, Finland: Welin-Goos, 1978)]:
 If communication can fail, it will.
 If a message can be understood in different ways, it will be understood in just that way which does the most harm.
 There is always somebody who knows better than you what you meant by your message.
 The more communication there is, the more difficult it is for communication to succeed.

These tongue-in-cheek maxims are not real principles; they simply humorously remind us of the difficulty of accurate communication. (See also A commentary of Wiio's laws by Jukka Korpela.)

It is contextual
In other words, communication does not happen in isolation. There is a:

 Psychological context, which is who you are and what you bring to the interaction. Your needs, desires, values, personality, etc., all form the psychological context. ('You' here refers to both participants in the interaction.)
 Relational context, which concerns your reactions to the other person--the 'mix'.
 Situational context deals with the psycho-social 'where' you are communicating. An interaction that takes place in a classroom will be very different from one that takes place in a bar.
 Environmental context deals with the physical 'where' you are communicating. Furniture, location, noise level, temperature, season, time of day, all are examples of factors in the environmental context.
 Cultural context includes all the learned behaviours and rules that affect the interaction. If you come from a culture (foreign or within your own country) where it is considered rude to make long, direct eye contact, you will out of politeness avoid eye contact. If the other person comes from a culture where long, direct eye contact signals trustworthiness, then we have in the cultural context a basis for misunderstanding.

This is the communication process:
 aim
 audience
 message
 mechanism
 result

To achieve quality communication you will need to:
 take the initiative
 be in control of the process