You ask some satisfied customers for testimonials, and you offer several of those as added evidence that you can and will keep the promise you made. If that isn't enough, you can a add moneyback guarantee or other reinforcement of your promise. There are usually several possible benefits that may be promised for any given product or service, and the key to success is finding and making the promise with the greatest appeal. In some cases, on promise will do well for everyone. Probably everyone will find the promised speed of relief appealing for antacid advertising.
Different people buy the same product or same kind of product for different reasons.
Some people will buy the least expensive automobile because they can't afford a more costly one, while others will buy it because they think an all automobiles cost too much to begin with and express protest this way, and still another party buys an automobile for his clerk to use for deliveries and sees no need for any but the most basic vehicle. The same consideration applies to proof. A significant element in the success of your marketing lies n finding the most effective proof to back up the most appealing promise.