Some people just seem to know everyone. They're networking rock stars. To achieve that legendary status among your contacts, try thinking of them as clusters.
If you expand your network based on the people you already know, you'll just bump into the same people. Instead, identify your network by clusters. Inc gives some examples:
Industries and subindustries
Entrepreneurs almost universally need the following types of introductions depending on the stage of their business and industry:
Peers & Mentors
Once you identify clusters, your first goal will be to connect complimentary clusters, like authors and agents. Along the way, you'll expand your network and help others at the same time. Check out the link for the full details on the cluster networking method.