Use Moz’s Link Explorer: Enter your competitor’s URL and you’ll find all sorts of data about their backlinks. Click on Linking Domains and a list of all the domains that they have secured links from will display for you. From here, review the links (click on the link to see the actual post) and see if there’s an opportunity for you to guest post with them as well. If your competitor’s site is linked to from this one, it may be a good possibility for you too.
Contributor: Rachel Lindteigen from EtchedMarketing.com