How To Write Good FB Ads?
It's all about doing what works
1). Start off with what is working for your competitors (both ad copy and images) as this is always a good place to start
2) Click out reviews both good and bad of the competitor. This will give you ideas for a USP and ideas for the ad body.
3). Find similar images to what the competitors are running or take a look at the fan pages, see what kind of images the fans engage with.
In the end. I don't know who said it. But always follow the money - in other words find out what works and make it better.
Same applies for fb ads as well as any other marketing your in.