A few years ago, at Colenso BBDO in Auckland, we got a call from Levi's. It was the head of marketing in San Francisco. He introduced himself to our receptionist. She was having a busy moment, heard him say 'Levi's', and put him through to Levi, one of our creatives. Levi came running into the office where I was sitting with our MD and ECD and told us there was a guy from Levi's on the phone wanting to talk to us. He handed us the phone.

The guy from Levi's said he'd seen our work, he loved it, and that he wanted us to make an online film for his new women's product line. He didn't have much money, but he wanted something amazing. And he said that we could do anything we wanted. Excepting doing something illegal or grossly offensive, we would have the decision on what work we made. He wanted our judgment on what was great and what would be seen and shared by his customers.

For a little agency in New Zealand, being called by Levi's global head office and asked to make whatever we wanted was pretty exciting. We said yes. A few weeks later we released a film called Rear View Girls showing a pair of models walking around LA with a hidden camera in the butt of their jeans. The footage caught guys (and the occasional girl) checking out the models' butts. We showed how great your butt looked in these new Levi's women's jeans.

It was powerful and hilarious and it spread like wildfire. Within a week, 10 million people had viewed the clip, and media around the world had shown and even parodied the video. Rear View Girls won a Silver Film Lion and became the most successful viral campaign ever for Levi's, anywhere in the world. The budget was £5,000. Meanwhile, in other areas of the agency, we had clients with real budgets buying safe ideas, watering them down as much as they could, and sending them out into the world to make barely any impact at all.

Of course, we presented great work to them. And we sold our hearts out. But the truth was, they hadn't decided they wanted great work when they wrote their brief. They didn't come to the creative presentation expecting work that made them nervous, or work that had the potential of wowing consumers. They came expecting work that clearly communicated the facts about their brand in a way that made them feel safe. And so all the salesmanship in the world didn't matter – they'd come in wanting one thing, and we were trying to give them another.

There's a popular myth in advertising. The myth of the suit who can sell anything to a client. The myth that with the right presentation, you can get any client to buy great work. The stories of Saatchis' suits in the 1980s being told not to come back until the work was sold. In my experience, it doesn't work like that. The sales job begins way earlier. If you're only starting to sell the client on a highly creative approach in the creative presentation, you've missed the boat.

The best way to sell great work is to have the client come into the agency wanting it in the first place. Like Levi's did. The reason most clients don't is simple: they're conditioned to see great work as abnormal. Out of every 7,000 campaigns produced, one is creatively awarded. Clients aren't like us. They don't spend their days poring over awards annuals and looking at what's won at Cannes. They live in the normal world where advertising is overwhelmingly safe and dull. Us agency folk spend more time looking at great advertising than everyday advertising, so we think great advertising is normal. Clients spend more time looking at bland, dull, everyday advertising, so they think that's normal, that's what's acceptable, that's what's politically 'safe'. And so that's what they come into the agency looking for.

There's a simple way to overcome this. You have to tip the balance in the client's head. You have to feed their head so full of great work that they see more of it than they do everyday advertising. So great work gets normalised. How? By spending time with them, long before they've written you a brief, showing great work, talking about it, inspiring them about its effects.

In January, with the help of Warc, The Gunn Report and I released our annual 'Cases for Creativity' – a round-up of the campaigns that won both a Gold Lion for creativity and a Gold Effie for effectiveness. It's a good place to start. The hope is that agencies use those campaigns as a way to inspire clients to want to do better work. And that more clients do like Levi's and walk in wanting it.