Marc, no problem on the question. I'm posting a reply to your Private message here, because the PM wouldn't go back to you. I hope you get it.
I've had a lot of experience in this area.
Blanket statements like "Postcards are best" is not the best advice in the world

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Of course it takes testing. For some offers postcards may prove betters, some times self mailers, and some times letters.
I've had much more success with self mailers than postcards, and I mailed to the exact same list multiple times. What does that tell me?
Hmmm, not hard.
I can assure you that most people never use letters the way I've described, and so they can't say whether they are effective or not, can they?
There's a couple of ways to get your mail opened. There is a long line of data and statistics pointing to letters as a better way to get response than postcards, but for your question specifically, I'll address that.
What is your target's biggest PROBLEM when it comes to what you offer. Is it too expensive? Too complicated? Scary? Confusing, Frustrating?
After you have identified what you most often hear in terms of a problem, (from your clients) then turn
that into a headline.
I'll use price because that tends to be a popular way that we agents sell ourselves.
"How A Legal IRS Loophole Allows Angelina Jolie To Save 27% on Her Health Insurance Premiums...And You Can Too!" OPEN TO LEARN MORE...
Then I would go into how the IRS allows business owners to write off 100% of their health and dental insurance premiums.
Why Angelina Jolie? 2 REALLY good reasons. (She's a business owner of some type so that's the tie in.)
1. She's a hot superstar and you can put her picture in there to capture attention.
2. She is in a movie right now that is doing a ton of marketing, and you'll be able to leverage their marketing to enhance yours.
Now you will show them how they can set up a company that will only cost them $12 per year to maintain and it will save them hundreds, even thousands in taxes over the course of the year, or several years. (of course hypothetical, but you get the idea.)
Another example headline would be "How Savvy Americans (use your specific city for a better effect) Are Beating The Skyrocketing health insurance Costs." Open to learn more...
Also, have you downloaded the 100 Power Headlines and 32 Great Headline Templates from our video site?
Insurance Marketing Mavericks
If not, it will be a great help to you, watch the video on Copywriting for maximum lead attraction or (maximum response), put in your email address and go download the tools.
Don't worry, I'm not going to spam you. But I am giving a lot of value, and I need an email address to update people on the new content we put up. (For those who are offended...don't do it.

)
Hope that helps,
Beach Broker