First, we need to define the true purpose of a headline. An effective headline will do many things at once. It will attract the readers attention, convey benefit by appealing to the readers self interest and it will set the expectation for what is to come. An effective headline will also serve as a filter, selecting the correct audience for the copy that follows. First and foremost, an effective headline must be believable.
Most people believe that if it sounds too good to be true, it probably is.
In the headline, they will most likely scare your potential customer away before you have had the chance to explain why these miracles will occur. Effective headlines are short. They use them because peoples attention span is generally short, sound bites are memorable. A good headline is like a good sound bite, short and memorable. To shorten your headlines, eliminate adverbs and adjectives, save them for the ad copy where they can be justified.