Social networks are built to be viral.
You can use its viral nature to rapidly build your own personal network within the greater social network
Step 1 of your social networking plan should be to make friends with other network members.
Step 2 is to go viral and make friends with your friend's friends.
Social networks are inherently viral in nature in that when you send a public message to a friend, that message can be seen by all your friend's friends. This means that your message to a hundred friends may be seen by a thousand people. That's an incredibly viral tool.
It also makes it very easy to become friends with your friend's friends because the network identifies you as a mutual friend. This makes it easy for your friend's friends to accept your friend request.
The cornerstone of your social networking marketing is to build a large friend list. Not only can you communicate directly with your friends but you can also send a viral message through each friend's network.
So step two of your social network strategy is to send public messages to your friends that can be seen by each friend's network of friends.
(I wish there was a word that meant friend's friends :)