Headlines can do several things. They get people to read further. They let people know they're in the right place. They put people in the right frame of mind. They get people to read your ad or click on a search result. A good headline is one part in the process of persuasion. A bad headline is a quick good bye.
I found this article at GrokDotCom,
3 steps for writing (and testing) great headlines. The post defines the 3 steps as
Step 1. Scent
Step 2. Angle of Approach
Step 3. Wordsmithing
There's advice for each step and then lists of links for further reading.
From experience as a reader I can tell you headlines are extremely important. I'm subscribed to a few hundred blogs and there's no way I can read every post on every blog. I use my feedreader to scan headlines and those that interest me I click into the post. If a headline doesn't grab me in about a second I'll likely never read the content of the post.
As a writer I can also tell you how a better headline leads to more traffic. There are ways to get your readers to click and ways to get more search traffic all from a headline.
You might want to bookmark the post above. I've read many of the posts it links to over the years and I know they offer solid advice to improve your headlines.
Do you have any of your own tips on writing good headlines? Any questions for how you can improve the ones you write?