One of my favorite headline tactics is to connote something shocking, weird, confusing, odd, outrageous, or interesting. And then to explain it further in the copy.
You start with something that might seem unbelievable but doesn't tell the full story, which forces the reader into the copy to know more.
Let's say you sell a weightloss program. Your copy hinges on the idea that strict diets are bad. They slow down a dieter's metabolism and can even cause health problems.
The headline could say something like, “Fact! Most ‘healthy' diets are cold-blooded killers.” (The point is that strict diets “kill” your metabolism so to speak, but it's enough to pique the target reader's curiosity and pull then into your copy.)

Michel Fortin is a senior marketing specialist, renowned copywriter, and digital marketing expert. For the better part of 30 years, he's produced countless successful marketing communications and profitable campaigns that generated in excess of $300 million in sales. He's broken many industry sales records, including being instrumental behind the first ever “million-dollar day” online marketing campaign in 2004. He's worked with thousands of businesses and entrepreneurs around the world in a wide variety of industries on building their businesses, improving their marketing, and increasing their profits. He's a published author and often speaks at industry events. To connect with him, visit his LinkedIn profile where he is most active.