You should look and see what backlinks are pointing to your competitors. There are websites that can help you do that: MajesticSEO and Open Site Explorer are just two of them. If you find some authority sites you can visit them to see whether the content on your website would be relevant, and if it is you can create backlinks.
The other thing you can do is set up Google Alerts for your website. Every time it gets a mention you will get an alert and you can check to see whether that alert links back to your website – in many cases mentions are unattributed and these are wasted opportunities. If you find that the mention doesn’t lead back to you get in touch with the site’s owner or manager and have them create a link back to you.