One of the greatest sales copywriters who has ever lived was Gary Halbert. However, even Gary recognized that the quality of your sales copy was not the most important thing when planning a promotion.
The biggest success factor when planning a promotion is to make sure that you are talking to people who are actually interested in what you are trying to sell. It sounds simple, but many beginning marketers don't focus their promotions on the right people.
Gary uses the example of an amazing campaign that he could write for selling knitting machines. It would be as brilliant as Shakespeare. However, not something that most people would be interested in. If you sent that campaign to a group of knitters, then it would convert like crazy, but for you and me ... not interested.
However, if you were away from your wife and she was having a triplets, then it would not matter how the news was worded ... you would be mesmerized. If someone was trying to tell you what was going on with your wife in broken English ... you would pay attention.
That is because knitting machines don't matter to you, but your new triplets do.
60% of the success in any promotion is who you are talking to (the list). 30% is in how good the offer is. Only 10% is based on how good the copywriting is.
If you have a targeted list and a compelling offer, then anyone can sell it.
