Hi Rich

Tom's method is good, but I find that a lot of opportunities arrise from smart interactions and engagement with bloggers on social media channels.

I always find that you're more likely to be allowed to do a guest post for a blog once you've built a relationship first. It's a good idea to research blogs you want to reach out to and then engage with them without asking for anything first. Then, once you/ your brand is on good terms, float the question.

This is also a powerful way to drive blog publicity in a more general way, without even needing to provide a guest post.