I do believe there is a nontrivial number of developers that work in a job well below their skill set, who just haven't gone out of their comfort zone to find a new job, or who haven't been discovered yet because they're so insular.

So instead of networking and the like, I'd start a bit earlier even: You don't have to settle for what you have right now. You can do better. An interview is not a job application you have to see through to the end, you don't owe them anything. Know your worth.