There is much stuff written about the role of co-citation for SEO. To explain co-citation briefly: if site A links to sites B and C, then Google means sites B and C are somehow related. But how SEO makes a valuable backlink Profit with co-citation?
How to use co-citation to get a high-valued backlink?
Content is surely a king;)
Conceptualize and write a serious article, where you explain, test and/or compare some high-ranking sites. services or products with your own (this is very important requirement - you must be in the same business segment to achive the most effect). Make an accent on strong aspects, touch on a topic pro's and contra's of using them. Arrange the whole article so, that it remains objective, but is engaging for the owners of tested services.
Extensice using of Microdata mark-up makes your article in general machine-readable and, further, helps Google to achive putting entities you are describing into correct relation to each other. On using Microdata make sure to show Google your targeted direction with using of such Product properties like sameAs, isRelatedTo, isSimilarTo. If you need a describing class transition from Service to Product, you can accomplish it through following chain: Service has a property "produces", which expected type is a Thing, and Product class is a subclass of the Thing.
Human factor still works!
After you get your writings done, put on your friendly make-up, if you are not friendly by nature, and contact owners of tested services, notify them about your article and ask nicely about (NO! Stop! Not about a backlink!!!) but about, what important aspects of products or services have you omitted in your test. After you complete your article, send them the updated version with a direct link and few info lines about the author: in 98% you promptly get a prominent backlink.