Before asking someone if they’d like to guest post on your site, open a valuable dialogue about something else with them first.
A concrete example of how to do this is as follows: Say you run a newsletter or blog regularly. Each time you publish, reach out to the people behind any products, articles, or resources that you mention, to tell them that you mentioned their stuff, in case they might want to share your blog, or just know about the mention. You’re doing them a bit of a favor by covering their creation, and another favor by letting them know. In the same email, you could mention the blog(s) you run, and tell them that you’d be open to explore collaborations in the future such as guest posts.
Another opener you could use would be to tell them you’ve read some of their recent blog posts, and to say something like if you’re anything like me, you’re constantly looking for ideas on what to blog about, so here are a few titles I thought would work for your blog, based on the stuff I read: X, Y and Z.
Contributor: Jói Sigurdsson founder of crankwheel.com