In Harvard Business Review,  Tuba Ustuner and David Godes point out that each stage of the sales cycle requires different social networks. .

Identify prospects: You need contacts who know different people in the target companies that would have an interest in the service you offer. Your contacts should know different people in lots of companies - not the same old gang of over contacted  buddies. Ongoing networking is required over a broad playing field. If you are in sales or business development, consider a company approved personal blog. I am finding this blog very useful for rapidly expanding my network

Gain buy-in and upselling: You need contacts within a target firm who will invest time educating you on the company and introduce you to others in the organization who can be of help. This  prospect network involves fewer people but with stronger ties. For upselling you need to find internal brokers who will provide contacts in their firm for further sales.

Create solutions: To land the account, you need to develop customized solutions. Try to mobilize a network of experts back in your own company who can work with the appropriate people in the target company - try to build  an intraorganizational network.

Close: Call upon past clients who can act as references for decision makers. This takes precision to engage the correct person. Take care that they are not overused.