Takes time—be prepared to devote significant time initially, and then regular time weekly, to your network. This is especially true when you’re in job search mode (thirty hours or more per week spent networking is not unusual when job searching, in order to be successful).
Requires taking notes, collecting business cards, and building up information in your contact manager (Outlook, LinkedIn or others), which also requires a significant and regular commitment of time.
Requires periodic contact with many of the people in your network. This can be in the form of emails, phone conversations, face-to-face meetings, and networking events.
Works best when you treat people as people (with their own hopes, dreams, hurts) and not simply as resources. Consider emailing an interesting link or a job opportunity to someone who might benefit from it, to send praise for an achievement, or to send a thank you for valuable assistance.
Will require face-to-face meetings (sometimes over coffee or lunch), phone calls, emails, and other personal contact with other people.
Remember, networking is about building relationships, not just building a collection of names and email addresses.