Our best hires are friends of our employees. In fact it works so well when we want to hire someone we think of job ads as a waste of time. And there is some explanation to that:

Good employees (and you'll surely have one) have friends on the same level. If your company / environment / team is good then employees are happy and try to convince their friends to join so that they can work together. We have 17 employees and only 3 of them have been hired through job ads.