Normally with copywriting it is all about the headline and then the copy. However if you are considering facebook advertising it is all about the image.
However when you think about it there is a fundamental difference from a Facebook user to a google searcher. One is (or you can determine) actively looking for information or to buy a product or solve a problem and the other is simply looking to hook up with friends and share their feelings/thoughts etc. The bottom line is this, you have no idea if they are looking to buy your product or service.
So you need to re-think your ads, you might not be able to sell them on your product or service but you might be able to get them to ‘Like’ your page which is setup specifically to promote your product or service. Once they are a fan you can then build that relationship and monetise later. The key here is, and my initial testing has found that you can significantly boost your click through rates, create a fan base and drive down your cost per clicks.