Your immediate audience is the person or persons to whom your communication is addressed.  Your primary audience is that person's colleagues or associates, or anyone else to whom the addressee might potentially show your communication.  Your secondary audience is anyone who will potentially be affected by your communication.

Say the Director of Procurement at a small private college asked you to prepare an energy supply plan in which you are to consider the technical, economic, and environmental implications of using a variety of fuels to heat the campus.

Your immediate audience is the Director of Procurement.  Your primary audience comprises the college president and anyone on the college staff who is involved in technical, economic, and environmental decision making.

Your secondary audience consists of students, faculty, alumni, and local residents.  Furthermore, should the college make a controversial choice based on your recommendation, other members of the secondary audience might include lawyers, the press, and the general public.

Although you have many different audiences to think about, you must without fail satisfy the needs of the person receiving your communication. 

If you know, however, that the person receiving your memo may well show it to certain other managers, you will probably want to keep that fact in the back of your mind.

And if you know that your memo could be leaked to the press or could become a matter of public record, you will certainly want to choose your words carefully so as not to give the general reader an incorrect impression of either you or your company.

People in your organization can use this simple tip to make sure they're sending the right message to the right audience and that their communication has no unforeseen consequences.