People prefer to do business with people they like. You should bear that in mind if you want to succeed.
And being liked involves not invading individuals' vital bubble.
Let me explain. This bubble is an Italian way of putting it. In this country we call it personal space.
That's the space around us that we only let those dearest to us inhabit - parents, partners, children, close friends; those we love and trust the most. As for strangers, we don't like it when they place their face and body uncomfortably close to ours.
Of course, there are occasions when we relax this rule. Like when we're standing in a packed tube train or celebrating a goal in a football stadium. But, generally, you only succeed in alienating people by invading their vital bubble.
More importantly, if you're a salesperson, you reduce your chances of being persuasive.
They may not be invasive, but there are other ways of putting people off that you should watch out for. We all have aspects of our personality that other people find irritating. I watched a TV programme recently about a football hooligan fresh out of prison. He had a well-meaning mentor to help him with the transition back to civilian life. Trouble was, he couldn't look anyone in the eye.
He'd have a lot more luck with potential employers if he didn't constantly give the impression of being a shady character not to be trusted.
But then, probably no one had told him about this particular habit. Which brings me to the solution.
A long time ago, a work colleague had such bad body odour that people who shared his work space complained to me. So I sat him down in my office. At some distance, obviously. Treading carefully and with as much tact and compassion as I could muster, I presented him with a stick of deodorant and suggested he may like to use it.
To his credit, he refrained from using it on me and seemed genuinely touched. However, a week later the smell was still as bad, so he obviously wasn't touched by it all.
So, given that the subtle approach doesn't always work, here's what you have to do to be liked by more people, become more persuasive and influential. Ask the friends you trust the most to reveal your most irritating traits. They need to be sincere, honest, genuine and blunt.
Ask them to pull no punches. Then resist the temptation to throw one. That's not a good trait either. And then try to stop doing all the things that annoy them. Willing to try?
Philip Hesketh is a professional speaker on the psychology of persuasion and the author of Life's A Game So Fix The Odds.