I once watched a television programme on which some successful retailers were asked how they managed to choose good frontline staff for their stores.
One of their answers struck me as being both very simple and very wise.
The person said: "When I interview someone, I make a mental note of how often they smile. If they smile enough, I hire them."
Powerful sales pitch
I was reminded of those words last week during a trekking holiday in the Langtang region of Nepal.
One evening, after a magnificent but tiring day's hiking, my friends and I arrived at a mountain village where we planned to spend the night.
There were many hostels there, all of which seemed to be competing for the patronage of a small number of guests.
Our guide had pre-booked our accommodation, but the hostel owners did not know this.
Some of them called out to us as we passed, hoping to persuade us to stay the night - or at least to buy chocolate bars and drinks from them.
As we passed one hostel, a young woman delivered the most powerful sales pitch I have ever seen.
She stood in her doorway and, without saying a word, fixed each of us, in turn, with a broad, beautiful smile.
I was at the back of my group and had no choice but to follow my friends as they trooped on past.
But if I had had the opportunity, I would most certainly have stopped and bought something - anything - from her.
A smile will do it every time for me.
Service with a smile
I spend half of my life in coffee shops.
I do most of my writing in them.
And although I live in a city with hundreds of coffee shops to choose from, I almost always plump for the same one - the one where the staff never fail to greet me with a smile.
Sometimes, I do relief teaching at a local school.
And although I try to be very professional, treat all pupils the same and not have any favourites, I cannot help but feel a special connection to those with friendly smiles.
A smile is a very powerful thing.
It creates a wonderful first impression and improves the quality of personal and professional interactions.
In a study last year, researchers Eugene Kim and David Yoon, from the Georgia Institute of Technology in the United States, found that retail employees who smiled at their customers tended to elicit positive emotional responses from them.
The improved mood of the customers then fed back to the employees themselves, putting them in a better mood too.
So service with a smile made shopping a more enjoyable experience for both employees and customers; for smile givers and smile receivers alike.
So why do people respond so well to smiles?
Well, I think that the French author Andre Maurois got it about right when he said: "Smile, for everyone lacks self-confidence and more than any other one thing, a smile reassures them."
We all want to feel liked, welcomed and appreciated.
And an easy, natural-looking smile makes us feel all of those things.
If you can, smile at will
Since I am such a huge fan of smiles and of smiley people, you might think that I spend my life beaming benignly at everyone I meet.
But sadly, that is not so.
I am one of those unfortunate souls who cannot smile to order.
If I try to manufacture a friendly smile, it comes across as a hideous grimace or a maniacal leer.
For me, if a smile does not come naturally, then it had better not come at all.
So if you are lucky enough to have a naturally smiley face, or the ability to flash a big old grin at will, I envy you.
You have a rare and valuable gift.
Make the most of it.
Gary Hayden is a philosophy and science writer.
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