It is birthday season for West End musicals. This month alone, Les Misérables has turned 22; The Phantom of the Opera has turned 21; Wicked and Monty Python’s Spamalot have reached their first anniversary, while next month Chicago turns ten.

Death of the West End? Nobody told these shows. Thanks to the impact of megamusicals such as these, The Sound of Music and Billy Elliot, the West End now sells more tickets than Broadway.

But intense competition and rising costs mean that, if you’re not a big hit, chances are you’re a big flop. “There are very few plays or musicals that are quite successful these days,” says Anthony Pye-Jeary, the managing director of the marketing company DeWynters. “It’s like being a bit pregnant.”

So this year The Drowsy Chaperone, Daddy Cool and Menopause the Musical have taken early baths. And even Wicked, playing to some 18,000 people a week, has not quite made its money back yet. The stakes are huge. A hot ticket for months? Pah! You need to be a hot ticket for years.

But how? How do you stop people thinking that they should have seen you with the first cast, when you were shiny and new? “It’s an awful lot of work every day,” admits Michael McCabe, the producer of Wicked. “I’ve been doing this for 25 years and it’s never been harder.”

Word of mouth, everyone agrees, is what all shows depend upon. But if that’s all it took, the two men who market almost every musical in town – Pye-Jeary, of DeWynters, and Adam Kenwright, the founder of AKA – wouldn’t work from such very nice West End offices. “Opening a musical,” Kenwright says, “is a bit like opening a restaurant in London and needing it to be as successful as the Ivy to survive.”

Having a good idea is only the start of it. What you really need is this: the ten surefire ways of making sure your musical runs forever.

Lure in the ladies

When was the last time a man organised a big trip to the theatre? (A straight man, anyway.) Particularly when it’s to see lots of soppy dancing, balladeering and (urgh!) kissing? “The man might make the decision to go to the theatre,” says Pye-Jeary, “but the woman will normally make the decision of what to see.” Women, once alerted to your show by your fiendishly focused marketing, are more likely to a) bother to pick up the phone to book in the first place; b) tell their friends; c) arrange said friends into a nice big group. (A third of Dirty Dancing’s and Billy Elliot’s business is from group bookings.)

“It’s not rocket science,” says Joseph Smith, the co-producer of Desperately Seeking Susan. “By far our biggest demographic is women over 35. If you want coach parties, you’ve got to get the female pound. As much as theatre is run by men, the people who really run it are the people who buy the tickets.”

K.I.S.S. (Keep it simple, stupid)

If you can’t sum up your £10 million spectacular in a breath, forget about it. Look at the success stories. Billy Elliot: boy dances his way out of Northern poverty during the miners’ strike. Wicked: how did the Wicked Witch of the West from The Wizard of Oz get so rotten? Cats: some actors mill around in cat costumes and sing (or something).

Now look at this year’s big dud. The Drowsy Chaperone: a modern-day musicals nut sits in his apartment and listens to a vinyl recording of a 1920s theatrical frolic. Hello? Hello? Are you still there? Actually, The Drowsy Chaperonewas bright, lavish and blissfully funny. But it closed within weeks because nobody knew what the hell it was.

“It was one of the toughest jobs we ever had,” Kenwright says. On Broadway, he explains, theatregoers will try out a new show willy-nilly. “Over here, when you’re up against Billy Elliot and The Lion King, it’s hard to get people to shows that don’t sell themselves in a single sentence.”

Image is everything

Again: simple, simple, simple. Les Mis has its urchin etching. Phantom has its mask (sometimes with a rose). Mamma Mia! has its beaming bride. And the daddy of them all, Cats, had a pair of dancing cat’s eyes. Pye-Jeary still remembers with pride the day in the early Eighties when he and his team decided that the image was so strong that they could remove the title from their bus ads. Cats productions around the world all went on to use the same image.

“You can’t get more than four words on a bus,” Pye-Jeary says. “I always used to take the poster to Andrew [Lloyd Webber] and I would stand in the garden opposite and hold up my bus image, and he would glance out of his window and check to see if the image made an impact from that far away. Cameron [Mackintosh] actually comes to the bus depot!”

Keep ’em keen

“If you want a long run,” says McCabe, the producer of Wicked, “people have got to come more than once. If you’re a ‘well, that was great but I wouldn’t go again’ kind of musical, you’re in for a hard time.” Wicked has fans who come back every time there’s a cast change, he says. And repeat visitors often bring new friends or family with them.

Plus, if you can add a new famous face as well, recasting looks like an act of rejuvenation. “One of the ways we keep our show fresh is to put new stars in the parts,” says David Gluck, the general manager of Chicago. Mama Morton has been played by everyone from a 22-year-old Kelly Osbourne to a 54-year-old Lynda Carter; Billy Flynn has been played by everyone from Marti Pellow to Sacha Distel. “New stars tend to attract people particularly interested in them,” Gluck says. “It’s like opening a new show all the time.”

Arrive with a fanfare

You have to exude a winner’s confidence before you even open. Shows playing big theatres will spend at least £1 million on marketing alone in advance of opening. Smaller musicals may spend £600,000 or £700,000. That means serious forward planning. “Ideally, we’d have eight or nine months before a show opens,” Kenwright says. “We’ve been preparing for Hairspray since it opened on Broadway.”

Pye-Jeary normally becomes involved when a show finds its theatre. “A poster,” he says, “can take six days or six months. Often Andrew [Lloyd Webber] will play me the music before the show is finished.”

Have deep pockets

OK, you know you’ll need millions for that quarter-scale Niagara Falls set and to pay the cast. But, even after you open, the chances are that you’ll be spending £25,000 to £30,000 on marketing alone every week. Or even more to pump-prime trade during the dips around April (Easter holidays) and September (back-to-school time). Yes, you could make your money back in six or seven months if you sell out every night. But with 26 other musicals to compete against, only Freddie Mercury joining the cast of We Will Rock You could guarantee that sort of business.

“We never, ever budget for a show to take more than about 80 per cent,” says Nick Allott, the managing director of Cameron Mackintosh Ltd – the producers of Phantom, Cats and Mary Poppins. “People who budget for takings of 90 to 95 per cent capacity are suicidally confident.

“Word of mouth is the best way to sell, but you need patience and deep pockets. Those who went to The Drowsy Chaperone loved it. If it were being produced by a man with bottomless pockets, it would be running now and pulling in good houses.”

Don’t look bored

How can actors possibly stay interested doing the same stuff night after night after night? “A lot of the people who say to me, ‘How can you do the same thing every night?’ are people who spend their every day sat behind the same desk,” says Tim Stanley, who joined the cast of Mamma Mia! in February 2000.

Stanley is part of the ensemble – but also has the more sergeant-majorish job of dance captain. “Performers have to be reminded occasionally that people haven’t seen the show before,” he says, “but not as often as you think. When you’ve got a full house, 1,100 people on their feet dancing, that’s a pretty powerful motivator.”

Stanley is booked until March – and hopes for a year’s extension after that. “We must be doing something right,” he says. “Forty per cent of our business is return business.”

Get good reviews

Well, duh. But it’s not just theatre critics who can boost your show. The takings for Wicked, McCabe says, soared after Phillip Schofield enthused about it on This Morning. “That’s like gold dust, a recommendation from someone whom the public trust.” We Will Rock Yougot a slating from puny critics. Chris Tarrant, though, gave it the thumbs-up. His quote was slapped on the hoarding and, five years later, it’s still, it’s still rocking us.

Billy Elliot recently had its 1,000th performance, but its producers still look for feedback. They leave a leaflet on each seat inviting the audience to take part in a telephone survey saying what they thought of the show. No nude salsa routines have been shoehorned in as the result of a punter’s suggestion, alas.

But producers find out who their customers are. “Also,” says Joseph Smith, a co-producer, “a show that runs three years will always deviate from its original construct. So if someone says, ‘Billy dances too well at the beginning’, you might follow up on that.”

Think outside the box office

Spamalot is fun for all the family. But it is not, strangely enough, an easy sell. “Look at the title,” says its marketing manager, Crispin Ollington. “Monty Python’s Spamalot. Well, Monty Python isn’t everyone’s cup of tea. A lot of people will reject it out of hand. Spamalot,what’s that? It’s an in-joke. ‘Knights, eh?’ Men in tights. It’s a male show and the classic West End demographic is female.” So Spamalot has to act frisky. Soon the producers will launch their own reality show to cast a new leading lady. In Sweden. “Sweden has a strong tradition of musical theatre,” Ollington says, “it’s not as if we’re going to Turkmenistan.”

Reality shows, he admits, are the ultimate marketing device: “Trying to create this communal experience is the future. But if you were doing it in the UK, you couldn’t compete with Joseph or Maria. You’d end up on Channel 5 or VH-1.”

Gimmicks are not enough

Disregard all facile ten-point plans. “If anybody says they know the secret of a hit musical,” Pye-Jeary says, “they’re lying. We all want to know that.” Best, then, to find a show that you’re bananas about rather than cynical about. “The musicals selected by focus group – Winston Churchill, Robin Hood, Sherlock Holmes, Joan of Arc – gone! Disaster! What focus group would say, set T. S. Eliot’s Old Possum’s Book of Practical Cats to music? The unknown wife of an Argentinian dictator? A Victor Hugo novel? Shocking ideas for musicals!”

Good ideas, suggests Pye-Jeary, matter far less than good structure. There comes a point when all the Facebook pokes and VIP ticket deals in the world can’t keep alive a dying show. As the producer Raymond Gubbay once said: “If the public don’t want to see something, there’s no stopping them.”

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010