If he'd asked me 10 years ago, when I was still in the profession, it would have been easy: I would have told him always to carry a Twix in his top pocket and never to volunteer to do the white elephant stall. You can't imagine Socrates or Thomas Arnold giving up a Saturday afternoon to lurk sheepishly behind a trestle table laden with chipped porcelain ballerinas, lethal lamps made from Chianti bottles, rusting woks and a heap of Demis Roussos albums. It's particularly embarrassing when a child points you out to his Mum. "That's Mr Evans who teaches me English."
What can make it unbearable is the abject pity in the mother's eyes. She doesn't expect her GP, solicitor, accountant, hairdresser or any of her friends to have to spend Saturday afternoon begging for a few extra coppers, and can't quite understand why an English teacher should be doing so.
It might even cross her mind that it would make better sense if he were at home marking her son's exercise book. It's at moments like this - and there are many in the course of a teacher's week - that a comforting mouthful of Twix can do much to rouse the sinking spirit.
I munched through miles of the stuff during the 18 years that I spent as a teacher - years in which I grew increasingly baffled by the complexities of the job. Then I left the profession to seek fame and fortune as a writer with a capital W. I never quite made Broadway or the Booker, but I've been happy to settle for being the dork who allowed himself to be photographed with a globe on the end of his finger. You'll be glad to hear that I have cold turkeyed on the Twix and that something even more remarkable has happened.
As caterpillars emerge as butterflies, the baffled teacher that I once was has become an educational guru. I was thrilled to hear myself using phrases that had never before graced my lips. "What schools should be doing I The trouble with education is ... What teachers should realise I" I was gratified to discover that, although I'd only ever taught English, my new-found expertise embraced every subject on the curriculum and every facet of school life. There was no educational problem so intractable that I did not have a smug solution.
The miracle I have experienced illustrates a fundamental truth: the longer you've been away from education, the easier it is to sound off about it. And, it follows that those who have never taught know best of all. It explains why GPs, solicitors, accountants, hairdressers and all your friends are happy to tell you what's what when it comes to schooling, but would be affronted if you ever had the temerity to tell them how to do their jobs. Similarly, news-paper pundits know precisely how children should be taught, simply because they have never had to try to do it. Of course, the real experts are the politicians who would never dream of clouding their judgment by doing anything as rash as set foot inside a classroom - unless it was for a photo-opportunity.
So if the young probationer really wants to know how to teach, my advice would be to keep well away from schools. Instead he should join the Office for Standards in Education or the Department for Education and Employment - or try his luck at balancing a globe on the end of his finger.