Networking is all about communication and building relationships with people, so there are some favourite methods that are always relevant:
Meeting people one-to-one or at events. Even one meeting usually makes it much easier to follow through with other ways of communicating, because you have more “feel” about the other person and their preferences. See the [People] section.
Phone calls whether one-to-one or on a conference call. Some people are happy to take a call on their landline or mobile anytime … while others like to manage their contact with others. If you know someone uses email a lot, you can send a message asking when it is convenient to call.
Newsletters, to keep people in touch with what you are doing, are essential for networks, whether printed, via email, or both. However, newsletter are essentially one-way, and if they are the main means of communication can make the network essentially hierarchical: see the Structures section.
Email and other online tools are very valuable for networking - but only, of course, if you and your contacts are online. As such they can be divisive if some people are connected and others aren't. If that is the case, you may be able to find “connectors” - people who are connected who will spread information more widely by other means.
In addition, in order to keep in touch you'll need a good contacts book or database, a full diary … but more than anything an attitude that's open and friendly, with a commitment to offer something to those you meet as well as ask. See online methods
The A-Z section covers some of the key ideas behind networking, and has more on some of the methods. See also the Resources sections.