Philip Hesketh says just a single unwise comment could move you from hero to zero in the eyes of colleagues and clients

Networking. These days, it's a popular way to build up business contacts and establish relationships with potential clients. It's a bit like speed-dating but with laptops. Instead of discovering whether someone shares our love of the theatre or fine wine, we want to know their business plan for the next 12 months. But just how much should we reveal about ourselves to new-found friends? And how far can you take a business relationship before it become counter productive?

A recent study from Harvard Business School casts doubt on the theory that the more you and your business colleagues know about each other, the stronger the relationship. Familiarity, it seems, really does breed contempt. Not surprisingly, when asked, 80% of businessmen said they preferred to do business with people they know. Better the devil, and all that. But when they were shown a series of general traits broadly representative of businessmen just like them, the more characteristics they were shown, the less they liked the theoretical individuals.

But why should this be? The answer, according to the researchers, is that the more we discover about a person, the more chance of uncovering a trait we don't like. And once we do that, it colours our view of that person, regardless of all the other positive traits we admire. So, for example, you might not want to reveal you're a Man U fan when trying to get a sale on Merseyside. Or you like to go seal clubbing in the winter with old university chums. The moment you reveal something about yourself that others don't like, it's downhill all the way.

Recent events bear this out. Fat cat company directors of failing financial institutions go from hero to zero before you can say one million pound pension pay-off. We are seeing right now that MPs can undo a lifetime of achievement when it's suddenly revealed that they've been claiming for a Peruvian foot slave to clip their toe nails twice a week.

As I say in my Desiderata: never outstay your welcome; guests and fish both begin to smell after three days. So next time you are at a conference with various business associates, give them a bit of space and make yourself scarce for at least part of it. Once they see an unlikeable trait during their conversation with you it will negatively affect the way they perceive the rest of your traits; even things about you they might have liked.

And on no account tell that hilarious anecdote about the mystery couple you discovered in a laundry closet at last year's event. You just never know who might not find it funny.

Philip Hesketh is a professional speaker on the psychology of persuasion and author of the Amazon number one bestselling book Life's A Game So Fix The Odds.