Social networks differ in terms of their offerings and services, but they all have one thing in common: words. The right caption or call-to-action is more than just the icing on the cake, it's the moment of connection between user to user. That's why it's crucial to know how to write well for each of the mediums. What makes great copy in one service is likely not great copy in another. Instagram, for example, is not the home of opinion or editorial -- but a blog is. Likewise, an email promo can be sales-oriented, while an email newsletter should be more low-key. It can be a bit dizzying. Fortunately, the folks at Vertical Response have provided a handy infographic that tells us how to write killer copy for each network.