Online Business Networking

Finding a place to network
Depending on how you wish to network, you can find networks to join in a number of ways. The most effective would be to ask people you know on or off the web if they recommend any good networks. For example, if you're a web designer in Manhattan, your colleagues might tell you about the World Wide Web Artists Consortium mailing list - an industry related network that has been in existence for many years, based in NYC. If you know another business person who operates online, they might tell you to check out Ryze.
Get on Google.com and do some searches for keywords like "forum" or "discussion board" and include your industry or interests in the search. For example, if you are a freelance writer, you might search Google for "freelance business forum" or "writers mailing list." It really depends on what you want to accomplish, who you want to network with (colleagues? prospective clients?).
For mailing lists, there are sites like Topica.com and Liszt.com that categorize the millions of mailing lists, which you can search to find some potential places to network.
Just because you find a network doesn't mean you will necessarily want to join it. For discussion forums, look at participation. How much traffic does the site seem to get? And how many, and how recent, were the posts? Don't waste your time joining if it doesn't seem like anyone ever comes there. You cannot gauge the traffic on mailing lists as easily so you will have to subscribe and see what comes through before determining if it will benefit you.
Getting Started
You can join a mailing list either by filling out a form on a web site with your email address, or sending an email to a subscription address. You will usually get a confirmation that you need to reply to, in order to be subscribed. Then you should get a welcome message telling you the basics of using that particular mailing list - how to post to the list, how to unsubscribe, and who to contact if you have problems. After you have subscribed, you will start to get emails from the list.
Whether or not you are networking via a mailing list, you should always have a "sig" file for your email account. A sig, or signature, is simply a bit of information about your business and contact information that is automatically appended to the end of every email you send out. It is set up in the options or preferences of your email application. For networking, it is essential that you set up a 2-4 line sig for anyone who wants to contact you, know what you do or find your web site.
For discussion forums, you can usually read posts as a guest, but to contribute, you will have to register. Registering usually involves filling out a form and answering questions about your business, and providing contact information. Be cautious what you provide here - you may want to include your web site address and phone number, but don't post things like your street address. If there is a description or bio field, fill it out - this is how people learn about you and what you do.
How to participate
Before entering into a discussion, it is a good idea to observe for a while. Get a feel for the types of people who are participating, what the communication style is, and the personality of the group. It is no different from face to face networking - you wouldn't want to wear a suit to a surfer's convention, or show up loud and brash at a chamber of commerce meeting.
For discussion forums, look around to see if there is a link to Frequently Asked Questions (FAQ) and read it. It may provide essential information about what is acceptable behavior or discourse, and tips for interacting with the group. You might also find a link or address to speak with the moderator or list owner, either on the web site or in the welcome email. This is a good person to contact with any questions or concerns.
One way to begin is to scan for questions that other members ask, which you can answer. Make yourself useful, helpful and share what you know. This is a great way to establish yourself as an expert, and get your name (and that sig you created!) out in front of the group. Once you feel comfortable, and have established some rapport, add your own questions, comments and concerns to the list or forum, and continue to do so over time. You might also notice, after observing a while, that new members post a short intro about themselves and you may want to do something like that too.
One of the most critical things to know about networking online is that the sales and advertising aspect of it is very subtle. DO NOT go leaping into a forum or list promoting yourself or your business directly. This will not win you respect or positive attention because if everyone did that, the group would deteriorate completely (as many have). Let your knowledge and your willingness to help others be your billboard and over time, you will establish trust and understanding among the group members about what you do, and what you are looking for.
If you aren't well versed in netiquette, it is more important than ever that you brush up on the basic rules. For example, typing in caps means you are shouting - so make sure you don't do that! Trim the email or post you are replying to, so it only includes the essential bits of the previous writer's post, and your reply. Don't post or send anything to the whole list which was sent to you privately without the sender's permission. There are many simple "golden rule" behaviors you should become familiar with, before networking online, or else you run the risk of making a bad impression or worse, alienating potential contacts. Don't worry though - there are literally thousands of netiquette sites online that you can search for and review, to get the hang of it.