When it comes to sales, you can't settle for mastering product knowledge.That's too myopic. You have to broaden your approach to include a comprehensive knowledge and expertise, not just of a particular product, but of the whole industry or field of which your product is one part. As Andy Frisella says, you have to be "the guy."  You yourself have to be a holistic resource for your customer. Those who do that will reap benefits for your brand and bottom line.