Believe it or not this is the simplest step. Simply use a directive. Qualified - and Blind. Which approach to use depends mainly on how well you are able to define your viewing audience and the nature of your product or service. The qualified ad is specific and includes more detail about the product you are selling.
Some products lend themselves to qualified ad content better than others.
Hair pieces for men is an example. Qualified ads will receive the least response but more of the responses which are received will result in sales. The partially qualified ad offers a special benefit, such as money or self- improvement. The readers have some idea of what you are offering, but don't know the specifics. If they are interested and desire your product they will follow your directive and send for more info.