Robert Chalmers doesn't like... 22 // Mwah, mwah

"Oh no," my colleague Jim whispered to me, as we stood in the school staff room in Manchester. "Oh, bloody hell." We were the last pair in a line of six or seven teachers, waiting to bid farewell to a Latina student who looked like a teenage Joan Collins.

I didn't need to ask what the problem was. She was working her way down the queue, planting double kisses on the cheeks of her former instructors. Ofelina came from Aguadulce, Panama. Jim comes from Hollinwood, near Oldham. I saw him glancing around for some means of escape. Unusual behaviour, you might argue. But the Islington kiss – the mwah! – hadn't and, so far as I know, still hasn't, become de rigeur in Oldham.

It's a trivial thing, I know, but air kissing strangers is one of those aspects of etiquette that you have no chance of avoiding even if, every time it happens, you, like me, are put in mind of the song Randy Newman composed, on a more intimate subject, called: "I think I've Been Doing It Wrong."

Jo Bryant, Debrett's etiquette adviser, has been quoted as recommending people "not to leave a saliva trace" (sound advice in most situations, unless you're a beagle); not to "allow a hand to wander" and "not to make any "mwah!" noises.

Mwah! has been in the dictionary for a few years now and, as any fan of Come Dine With Me could tell you, it's begun to contaminate places like Carlisle.

Etiquette changes, of course, and whining about it is about as much use as complaining about split infinitives, or how nobody except you understands the true meaning of "disinterested," and that "people are hanged; meat is hung." These days it's not unusual to see women made to stand on the Tube, even if they're pregnant. (To be fair on this last point, there's always a fear that, depending on how the standing woman is dressed, you may find yourself in the embarrassing position of offering your seat to a girl who just Really Likes Cake.) If you're the father, though, no such ambivalence applies. "There was a time," according to the US website Beautiful Births, "when expectant fathers were anxious, cigar-smoking men. Today's fathers," it boasts, "are very different."

For those of us not naturally cut out to witnessing what one friend described as "all that plumbing", the days of pacing the library, cradling a brandy, while the mother is assisted by somebody useful who isn't going to steal all her gas and air anaesthetic then pass out, are over. You're in there like it or not, even though, as I discovered with the birth of my first child, if something suddenly goes badly wrong, you're quite rightly elbowed aside and left sitting in a corner listening to the nurses' CD of Hotel California while the surgeons get on with the real work.

I was discussing the question of new conventions the other day with my colleague Virginia Ironside. "I get very cross," she told me, "when people ask if they can smoke in the garden when they come to my house. I prefer them to smoke inside. If they smoke in the garden a, there is a draught and b, I always think they are having more fun out there than I am, inside. I also get very annoyed when people try to take off their shoes when they come to my house. I don't like their smelly socks all over my carpets."

Staying with the socks, it's irritating enough when you knock on a door and hear that gentle yet forbidding welcome: "We take off our shoes in this house," somehow implying that you, for all they know, have spent the earlier part of the day behaving inappropriately with farmyard animals and haven't troubled to change your trainers.

People telling you what they should wear at your place, or where they should smoke, comes under the most annoying category of behaviour of all: Your House, My Rules. They'll extend this to telling you how much light you can have at the dinner table, which they prefer to be lit like Wembley Stadium, and the kind of music they like to hear when eating (none).

Happily, though, there are some habits you just can't change. I have a newspaper cutting describing an attempt by a fast food restaurant in Leeds to get their workers to tell customers to "have a nice day." This initiative had to be abandoned, the manager explained, "because the staff delivered the phrase in so dour and intimidating a tone of voice that it was tantamount to being told to f*** off."

Anyhow, do have a nice day. Even if you prefer to respond to this suggestion, as some do: "Thank you, but I have other plans."