My wife tells me she can tell what kind of mood I'm in before I open my mouth. She's usually right. That's body language for you. In every aspect of communication at work, whether it's the selection interview, the appraisal meeting, bargaining, counselling, presenting or at the board meeting, it helps to observe others carefully. This enables us understand better what they are feeling, as well as what they are really saying. It can also help us to ensure that the messages we wish to convey are, in fact, really hitting home.

Indeed much of the current interest in the topic of "emotional intelligence" - which is now regarded by many as a greater asset in business than one's I.Q. - is about reading the cues of non-verbal communication. Of course if such matters weren't important, it's doubtful whether politicians, the business world, diplomats and entertainers would flock so readily to workshops and gurus in the area of communications skills and body language.

Emphasising the relevance of the topic, one management training company argues: "an essential skill of the good manager nowadays is communication, and to be a good communicator you need to understand the effects and the power of your body language". It's estimated that about 80 per cent of the information we send out is non-verbal. So then, it's not the spoken word, but through eye contact, facial expression, posture, gestures and so forth that we actually "do the business". That is, whether it's persuading, delegating, negotiating, motivating, buying or selling, communication - of which body language is the biggest chunk - is crucial.

The experts tell us that the spoken word only accounts for 7 per cent, with intonation worth a further 13 per cent, leaving body language to do the vast majority of the communicating. However if you don't know about these messages, you have no control over the "vibes" they convey. Given that most of every manager's time is actually spent on communication, it may be time to start finding out.

Richard Denny, one of Britain's "gurus" on motivational public speaking, puts it all in perspective. He tells us that there are approximately 700,000 body language signals. In contrast, as far as the spoken word goes, there are approximately 40,000 words and sounds that can be used. However, in northern Europe we normally only use about 4,000 words on a day-to-day basis. Body language is also an important source of information in negotiations. Whether it's striking a pay deal, purchasing goods or services, or trying to gain the release of a hostage, it plays a crucial part. It is well known that in negotiations of consequence "observers" are frequently deployed to study the body language of their counterparts, in an effort to pick up vital clues.

Such is the relevance of the subject to everyday management activities that it regularly features on training programmes. Performance management consultants have now taken to advising managers on how to "listen skilfully" to their staff. Firstly they urge maintaining direct eye contact about 70 to 80 per cent of the time, while nodding periodically to send the (non-verbal) message: "Keep talking, I'm listening." They even advise that if you're not a natural nodder: "It's pretty easy to learn. Just stand in front of a mirror and start talking to yourself."

If you want to hold a listener's attention, whilst persuading them of the merit of your case, they also advise that you use your face - especially around your mouth and eyes. This area is filled with a rich array of muscles, which one should use when speaking: e.g. - smiling, wrinkling your forehead, widening your eyes, clenching your teeth and raising your eyebrows!

Job interview experts at www.iresign.com claim that a handshake can make all the difference at the crucial meeting. For example, sweaty palms may convey nerves. They recommend the use of the "bone-crushing" grip - which is probably appropriate if you're applying for a job as a bouncer or a prize fighter!

At the other extreme we have the "dead fish" handshake. This is where the interviewee offers the interviewer a limp, clammy hand which exerts no pressure. Apparently this shake is telling the interviewer that you have little or no real confidence and that you may find it very difficult to deal with people.

If you're looking for the "perfect handshake" they recommend that you "look the other person in the eye", whilst taking their hand. Next you press palm-to-palm and grip firmly - but not viciously! Then you smile, as you "pump your hand up and down". In the face of such advice one can easily see how interpreting body language can go dismally wrong. Indeed many contend that it is an area of dubious authenticity.

For example, in Britain recently a well-qualified black female teacher was discriminated against as a consequence of an "unsuccessful interview". Her problem was that she failed to make good eye contact with her interviewers. However the Employment Appeals Tribunal accepted the evidence that people of Afro-Carribean origin often avoided eye contact with those in authority. That is, in some cultures eye contact is regarded as impolite.

Despite the scope for misinterpreting body language, it is now widely accepted as an integral part of the communications process. Given that communication is the key feature of every manager's job, the skill of observing and interpreting body language, whilst controlling what is conveyed, would serve us well.

Wink, Wink; Nod, Nod. Know what I mean?

Dr Gerard McMahon is a lecturer in Human Resource Management at the Faculty of Business, Dublin Institute of Technology ppl1@indigo.ie