The Law of Seven is a selling strategy which states that the sale cannot be considered lost until at least seven sales attempts have been made. Or the converse, which states that the sale sometimes will not be made until at least seven exposures to the product are completed. The Law of Seven is followed faithfully by advertisers who continually pummel us over and over with the same ad to ensure that we have reached the saturation point of product recognition.
The same principle applies to networking. It is not enough to contact people once, then cross your fingers and hope something happens. Networking is more than making one call or sending an e-mail. You should regularly give your network contacts updated information on your job search and at the same time find out if they are aware of anything new. If you are actively pursuing employment, it's best to contact them once every two weeks. If you are passively seeking employment, once every one or two months is sufficient. And what if they remain "cold" after seven contacts? Remember that seven is merely the minimum for making full impact. Do not stop making contact unless you are asked to do so. Some of the very best contacts may be the most difficult to fully develop a networking relationship. Use personal discretion in making contact (one voicemail per week is max unless there is a critical timing need), yet make sure you do your part to keep in touch.
Let your contacts know when their help resulted in positive action. We all appreciate positive feedback, and when you express yours, it helps encourage even greater success in the future.