Find the sites linking to your competitors but not to you.
Just think about it: if a site is linking to every one of your competitors, what are the odds that they will link to you, too (once they find out you exist, of course)?
With the help of Ahrefs’ Link Intersect tool, you can easily find the sites that link to your competitors but don't link to you (yet).
Often your competitors will have “fans” who link to almost every new product or piece of content they release. You can easily discover who frequently links to your competitors by using this method.