18th birthday messages from parents, godparents and Nan

Most 18th birthday messages end with "wishing you health, happiness and every success". There's nothing wrong with it, but the birthday girl or boy will hear it twenty times that day and forget it by evening. What they'll remember is the one sentence where they recognise themselves.

A simple formula works: name → specific detail → wish. The detail is the thing nobody else could write — that at six they sold painted rocks outside the house, that they're the only one in the family who can parallel park, that they taught you a phone game you still don't understand. Then tie the wish to that detail, not to general "success in life".

The second thing is length. Two sentences are plenty on a gift card; a letter can take a page. If you have a lot to say, write it as a letter and put only a short version in the card — squeezing a whole letter in tiny writing onto a postcard does nobody any favours. And when you write their name, the Australian Government Style Manual adds 's even when the name ends in s: "For Thomas's birthday".

One more trap: lines like "now it's all up to you" and "time to finally start acting responsibly". An eighteen-year-old hears them as criticism. You can wish someone well for adult life without preaching.

If you're unsure of the tone, read the message aloud. If you stall or blush at the fake grandeur, they'll notice too. A message that sounds like you always beats one that sounds like a calendar.

Parents can afford the most feeling — and it still pays to leave room for humour. The examples work for a daughter or a son; just swap the names.

A godmother or godfather has the advantage of distance: they can be a bit of a rebel and a bit of an adviser. It's worth mentioning that they've been there from the very start — at the christening, or at the naming ceremony if they're a guideparent.

Grandparents are the only ones holding two generations' worth of perspective. The wording can be as old-fashioned as you like — grandkids expect it from you and love it.

Humour works when it's about the birthday person, not about drinking or getting old. It suits siblings, aunts, uncles and family friends.

The most common mistake is bringing up problems. "Just make sure you pass those final exams" may be well meant, but on the day of the party it sounds like a check-up. The same goes for comments about weight, looks, a partner or "who you were meant to be".

The second mistake is passing your own dreams on to them: "hope you study medicine like your dad". Eighteen is when a person is only starting to choose, and a wish that narrows that choice in advance isn't a gift.

The third mistake is drinking jokes. An 18th often comes with alcohol, but on a message from parents or grandparents that they might keep, it ages badly. Leave the jokes to their mates.

And finally: don't promise anything in the message you won't keep ("I'll never tell you what to do again"). An eighteen-year-old will remember it more precisely than you will.

A gift card usually ends up in the bin with the wrapping paper. If you want the message to last, write it somewhere it can still be found in ten years.

The simplest option is a book inscription — on the endpaper of a book they'll keep at home. Some parents go for nostalgia for an 18th: a personalised book in which the birthday person is the hero, drawn from their childhood photo, can carry the message as a printed dedication on the first page (the ebook costs A$11.99, the printed version A$54.99). How to write that kind of dedication is covered in Book inscriptions: what to write and common mistakes. Another option is a longer letter, which can also go into a time capsule — if you started one with your child years ago, an 18th is a natural day to open it.

If the message comes with money, add one sentence to the envelope about what it might be for. How to do it so the envelope gets more than a quick "thanks" is explained in How to give money so it doesn't vanish in a weekend. And if you're still looking for the gift itself, there are ideas in 18th birthday gifts for a son.

For most young people, eighteen is the line between childhood and adulthood: the age when they start making decisions in their own name and taking responsibility for them.

That's good material for a message, too. Instead of a general "adulthood", you can tie it to something real: a first contract in their own name, a driver's licence, a first trip without parents. A message that names an actual new freedom sounds more grown-up than one that just repeats the number 18.