Join your trade association and get to know your competitors. Make them your friends. That way you can refer business that isn’t right for you, or that you can’t handle, to them. In return, they will do the same for you.
Don’t waste a perfectly good networking event by spending all your time with people you already know. It’s okay to spend a few minutes socializing with your friends, but devote most of your time to meeting NEW people. That’s what you’re there for.