Move out of your parents' home Obvious, really. It's even better if you manage to get on the property ladder.
Dye your hair/have an unwise haircut/shave your head Often as part of an unwise identification with a particular style of music, such as punk, goth or Nu-metal.
Women: purchase your first pair of Manolo Blahnik or Jimmy Choo shoes. Men: purchase, then dispose of, some deeply unsuitable footwear Cowboy boots, winkle pickers, brothel creepers ...
Lose a fight After 30 you should be able to settle things amicably.
Attend a wedding/funeral of a contemporary Both important reminders of the fleeting nature of time.
Start writing a novel/film script/slim volume of deeply embarrassing poetry ... which will haunt you from the bottom drawer.
Spend a night sleeping outside Whether it's on a Greek beach, or in a London doorway after a particularly damaging night out.
Stay up for 48 hours Believe me, you will never be able to do this after you've turned 30.
Have your heart broken If this hasn't happened by the time you're 30, you're clearly emotionally subnormal.
Kill an animal A bird, a fish, a terminally ill family pet.
Drive a sports car extremely fast while wearing sunglasses Get it out of your system before the grey hairs appear.
Lose a week's wages in a casino See above.
Make your first million Wishful thinking, perhaps, but if you plan to be seriously rich, it's good to start early.
Have a pregnancy scare An important part of the emotional maturing process.
Have a one-night stand See above.
Have an office romance See above.
Have sex somewhere peculiar Aeroplane lav, boss's desk, pod on the London Eye, the central hall of Tate Modern ...
Be naked in public Streaking, skinny-dipping or just simple forgetfulness.
Have, at the very least, a flirtation with a minor celebrity It's important to be able to point at the television screen and say: "I've snogged him/her." NB this does not apply to Blue Peter pets.
Take a "work-break" to find yourself ... before succumbing to a life of soul-eroding wage slavery.
Have a quarter-life crisis Probably as a result of the above.
Do a McJob Something deeply menial but soul-improving.
Be so short of cash you have to sell something Record collection, family heirloom, kidney, sexual favours.
Work your way around Australia It takes a while, and you can't get a permit to do casual work once you're over 30. Other continents are also acceptable.
Grow out of cannabis Youthful experimentation is all very well, but a fuddled thirtysomething with a passion for Pink Floyd and a hunger for Frosties is just embarrassing.
Get arrested For a minor offence, obviously: something like disturbing the peace, which suggests you're not a terminal conformist. At the very least, you should have been breathalysed.
Get a tattoo Absurd if you're over 30.
Start your own dotcom ... and see it fail. You'll have a chance to bounce back into a proper job.
Drink yourself unconscious And wake up with only the haziest, shabbiest memories of the night before.
Have embarrassing photographs of you posted on a website by friends Possibly as a result of the above.