The whole "say-whatever-they-want-to-hear-and-we'll-sell-'em" mentality that still rules some corners of the marketing and ad industries just doesn't play anymore. Consumers are smart. They know when you're gaming them, when you're using a snake oil ploy just to make a sale. And, guess what, they're not buying it.
Think of your own "B.S. Alarm." Every time you see a shockingly low price followed by enough legal copy to send Matlock into convulsions, or every time you hear a claim in a commercial you know just isn't true, or every time some guy in a loud jacket tells you the extended warranty is worth every penny, "ding." The advertiser registers as one who speaks with forked tongue. You figure since you can't trust what they say, you can't trust anything else about them.
And trust, my delicate little flowers, is what this business is really all about.
The first step in creating believable advertising is to be transparent in your messaging. If you want to differentiate yourself from your competitors, don't do it in your advertising until you've done it in your product. Make it a meaningful difference, one that adds value. Then let your advertising messages simply (and honestly) dramatize that difference.
And if you're an ad agency, hold your clients' feet to the fire. If they want you to make claims that their product can cure premature baldness, don't be afraid to play the devil's advocate.
The key for marketers today is to cherish the relationship over the transaction. Customers want to trust you, but trust has to be earned. An important first step is to make sure that your messages honestly reflect who you really are, not who it's going to take to make a sale.