1. Buy a property
Buying whole buildings may be unrealistic - less than half of Londoners are expected to own their own homes by 2021. But with house prices predicted to rise 21 per cent in five years, property remains a great investment. Pool your pittance with friends and family for a hope of owning a room or two.
2. Have a baby (if you're a woman
We've all read those scary news stories - surely every 29-year-old is quaking with infertility fear? Now Beyoncé, our top role model, has got herself pre-30 pregnant. Time to follow suit.
3. Avoid having a baby
(if you're a man)
Male and female aspirations are rarely so divided as on the issue of whether trapping yourself in a 24/7 cycle of sleeplessness and regret is a good idea while you're still young.
4. Live abroad
A gap year after 30 is career suicide. Get South-East Asia out of your system.
5. Build your brand
No fibbing now - everyone has Googled themself. If you're not the top search result, something has gone wrong. Regular commenters on your blog and 1,000 Twitter followers are also essential.
6. Leave home
With rental prices up 14.5 per cent over the past year, leaving the parental home isn't easy - but life begins when you fly the nest.
7. Look after the pennies
You won't earn much interest but the sensible are saving for fantasies such as houses and retirement.
8. Drop out
So what if you still can't touch your toes? You can't let that stop you ditching your desk and becoming a yoga teacher. Escape the rat race before it gets you hooked.
9. Co-habit
Living alone is said to cost £3,500 more per year than sharing. But learning to live in harmony with boyfriends, girlfriends and friends takes practice. Test out potential partners now.
10. Have a threesome or a moresome
While legend suggests you may reach your "prime" in your thirties, you won't have the time or the energy for such adventurous antics. Indulge in a little sexual experimentation now.
11. Own a designer handbag
Be it Miu Miu and crafted from calf-skin or a classic Mulberry Bayswater, the perfect bag, paid for with your own hard-earned cash, equals job satisfaction by the bucketload.
12. Grow a pair
And learn to stand up for yourself. While your early twenties are all about "people pleasing", honing an ability to fight your own battles is essential. Learn how to say "no" and, more importantly, how to entertain the notion of being right.
13. Always wear sunscreen
Baz Luhrmann was right: with skin cancer now the most common form among twentysomethings, playing it safe in the sun is essential. And you'll be thankful for that wrinkle-free skin when you turn 40.
14. Dump the debt
Your days of student profligacy are long gone yet repayment letters are still coming as the interest on your debt increases. Whether it's the average £13,000 or £20,000, it's time to settle with the Student Loans Company.
15. Build up your black book
Information is power, and with it comes opportunity. In London, networking ability will always stand you in good stead.
16. Drop your last E
What seemed fun and "grown up" in your formative years will leave you tired - and possibly fired - in your thirties. Get it out your system while you can still cope with the hangover.
17. Be a fashion victim
What looks terrific when you're 21 will look tragic when you're 30. Indulge in flash-in-the-pan fashion trends while you still have the legs to do so.
18. Heal a broken heart
Understand the importance of a fully functioning, sanity-restoring relationship. What you wanted from love in your early twenties - fun and floppy hair - is no longer going to cut the mustard.
19. Get married
Jemima Khan was just 21 when she embarked on her "starter marriage" with Imran Khan, Lily Allen had hit 26 and Kate Middleton was 29 when she tied the knot. Start dropping hints now - but make sure you've got the £20,000 it normally costs to make it happen.
20. Take it to the extreme
Once you've climbed Everest, run a double marathon or done that sky dive you'll know you can push your body to its limit and still talk about it afterwards.
21. Write a book
Your expertise and ideas might be slim but you will never be as marketable again. Flaubert, Kafka, Fitzgerald, Updike and Walcott all pushed out classics before 30, so writing a decent tome is actually possible too.
22. Know who your friends are
Your 783 Facebook friends have already been winnowed to 638. As the job eats away at social time, loyalty and similar interests replace "seemed nice/fit in the smoking area" as the criteria for staying in touch.
23. Learn to cook
Still can't bake bread and struggling with béchamel? Take a cookery course, like Pippa Middleton, because chances are you'll be entertaining from now on.
24. Learn a language
Learning a foreign tongue when you're young is not only easier, it can also make you cleverer in other ways. Fewer than one in 10 British workers has managed it, though, so good luck.
25. Make a million
... or at least earn your age. Only the suited denizens of Canary Wharf and a few young Sugar-lings can hit the magic number so young, but hitting 30k by 30 has a nice ring to it.
26. Find yourself
The gap yah gag is largely funny because 18 is too young to think about anything meaningfully. However, 25 is not, and working out what you believe in should be wrapped up before family life takes over.
27. Have a summer of love
What is a proper summer without a new fling and a hedonistic trip to Glasto? Go before you start caring about hygiene.
28. Get a second life
Don't let work become life. Extracurricular activities could also help you unearth your real passion. Start a supper club, join a band or free-run through London.
29. Sleep when you're dead
Everyone knows the best fun starts after midnight. A hangover at work? So what, Alka-Seltzer is your friend …
30. Start a business
Four in 10 London undergraduates run their own businesses. Take the plunge while you still have nothing to lose.
