Literary qualifications have ...

Literary qualifications have no more to do with it than oratory has with salesmanship. One must be able to express himself briefly, clearly, and convincingly, just as a salesman must.
 Claude C. Hopkins

Quotes from the same author

Ads are not written to entertain. When they do, those entertainment seekers rare little likely to be the people whom you want. This is one of the greatest advertising faults. Ad writers abandon their part. They forgot they are salesmen and try to be performers. Instead of sales, they seek applause
 Claude C. Hopkins
The compass of accurate knowledge directs the shortest, safest, cheapest course to any destination
 Claude C. Hopkins
The only readers we get are people whom our subject interests. No one reads ads for amusement, long or short... Give them enough to take action
 Claude C. Hopkins