David Ogilvy is often referred to as the "Original Mad Man" and is surely someone you've come across before. If you've not read Ogilvy on Advertising, you should do so immediately - it's a timeless classic.
1 - Do your Homework
"Advertising people who ignore research are as dangerous as generals who ignore decodes of enemy signals."
You have to know the audience you're targeting - sounds obvious, but consider each customer (or perhaps segment) as an individual and talk to them simply, and directly. If you can't write a paragraph outlining what the customer you're trying to persuade looks like/needs/cares about, stop writing the ad and do it now.
2 - Don't talk down to them
"A consumer is not a moron. ... Don't insult her intelligence, and don't shock her."
Choose your language carefully - it should be the way the target customer talks and thinks, not the way you think your product should be described. Remember you probably need the sale more than they need to make the purchase - be humble in the way you communicate.
3 - Don't waste the headline
"Five times as many people read the headline than read the body copy."
Even more true today than when he wrote it - think 140 character tweet, video pre-roll, or PPC ad. Less than 10 words to get your message across and retain the customer's attention. This requires clarity and consistency across the whole journey. How are you going to re-enforce your message from a video ad on Facebook, to your branded search on Google? Cut the jargon and get to the point. One of the most useful tactics is to map your customer journeys so you can ensure you're delivering the right message at every step of the way. Check out some of the work we've been doing to help brands deliver better customer journeys here.
4 - Help the customer to buy your product
"The more informative your advertising, the more persuasive it will be.
If they're taking the time to read the second frame of your ad, you've probably got the targeting right and your headline was solid. Well done. Now's the hard bit - remind them why they should buy your product. Why is it an important product? How does it solve a need they have (whether they consciously know it or not yet)? Why should they buy it from you?
5 - Always be closing
If it doesn't sell, it isn't creative.
Don't get in your own way - remember why you spent so long ideating, designing and producing this set of adverts - to sell more products. Award-winning campaigns aren't just about the 'creative treatment', they're about driving profit. Every touchpoint in the customer journey is another opportunity to nudge the customer closer to a sale, don't waste it.
Visit the Fast Thinking Required Reading section to learn more from David Ogilvy amongst others, in our curated list of books, blogs and whitepapers we've been reading ourselves.