If you are not doing any testing, then a poorly performing headline is difficult to dissect. You can learn how to write effective headlines only if you study copywriting because that is where the roots are. Once you begin learning about it, then just take things one step at a time and learn the material and practice. We will move quickly into some proven tips for producing headlines that will work for you.
Just one approach with headlines that is universally powerful is stirring a desire to know more. There are many headlines that fail to grab attention and convert just because they don't bring out the curiosity in the reader. This is one factor that can get you more response than anything else because human beings are curious by nature and if you can target that emotion, you will see that more and more people are not only finding your headline interesting but are also reading further. First of all, you need to send the right people to your copy, and then your headline has to marry them to your content.
Keywords in your title or headline is important as well no matter where you are promoting your content. This is a practice that goes way back, and while a lot has changed it is still effective, or can be. But once again the issue of SEO writing versus writing for your audience comes into play. Just use them and make sure it reads well and totally normal, and you will be just fine.
Does what you have just written make you want to know more about the offer? Hopefully you have the ability to avoid playing games with your own self, and that is not always possible with some. If you aren't able to impress yourself with your headline then chances are that you won't be able to attract your target audience either. Maybe you have friends whom you can trust, but if not then just do not worry about it. There is a ton of great information available on the net about crafting headlines that work. Writing headlines is like writing copy in that you have to practice doing it in order to improve. Always strive to make things very easy for the reader so they do not get frustrated and leave. Be sure to write as many headlines for something as you can, and then keep working at it until the best one emerges.