As any good sales person knows the first rule is grabbing someone's attention. You have initially around 8 seconds in which to do this and then generally 5 minutes max to sell your idea.

People 'buy with their eyes' so having a good eye-catching first image that will show up in your preview is paramount and encourage readers to have a look, this is why lots of posts have what is known as clip bait but be careful, overdoing your images can start to irritate some people who maybe be more interested in being informed rather than looking at that rainbow coloured unicorn.

One of the other pitfalls I've seen is people writing too much content. While it's obvious a lot of work and research has gone into the article, after a while it becomes tl;dr

Such a shame a lot of the comments on this post are spam. :-(