Social networking sites such as Facebook and MySpace have become the party lines of this young century. They are inviting and intriguing and a powerful communication tool. Learning how to use them wisely for marketing can increase your business profile.

Jinan Wei, product manager at PR Web, an online press release marketing service, is a fan of social networking sites. He has formed a group on Facebook for PR Web that includes journalists, bloggers, and others in the media industry who uses PR Web as one of their sources for information. Rather than sending these group traditional, impersonal press releases, he uses it for smaller announcements. “If we’re going to have a booth at a trade show I’ll send out a note to the group and invite them to stop by,” he says. “Often someone will post a casual comment or ask a question. If it’s too long, I take the conversation offline.”

Wei is also a member on LinkedIn, which in contrast to MySpace and Facebook is used almost exclusively for professional networking. Users understand members sign up to promote themselves for career development first, their companies second. The quality of the network you create lies in the quality of the contacts, not the quantity. Krista Canfield, LinkedIn’s public relations manager, suggests you treat your contacts like you treat your Rolodex. “You wouldn’t hand over your Rolodex to everyone you meet at a conference,” she says, noting once you make a contact, that person has access to your network.

Once you’ve established a list, be judicious how you use it. You can send notes to your contacts but if you send too many, those notes are not as likely to get read or you might even be dropped as a contact. Use the list for small announcements: events, job openings, or vendor recommendations.

A secondary level for outreach is LinkedIn’s Groups. Currently there are more than 150,000 groups, including business forums, alumni groups, fan clubs, and conferences. If you run an interior design firm, or sell to interior design firms, you can choose from nearly 90 groups catering to that field. Some are credential-based; some are based on geography. The group “owner” approves your membership to ensure validity.

Another way to build your credibility on LinkedIn is by participating in its Answers forum. For instance if you are a travel agent you might want to visit the Business Travel section to see if you can give any advice. Canfield suggests using the soft sell. “Approach the discussion as you would at a business lunch,” she says. “You know people are there to further their businesses and make good contacts, but you need get to know them a bit before promoting your services.” Another tip: check out their public profile before engaging them in a conversation. Chances are you might have a connection, whether it’s a college, a personal interest, or a shared skill such as speaking the same foreign language.

For the long term, the value for marketing on social networking sites may be simply the ability to reach niche groups via advertising. Most of these sites have targeted text advertising with fees in reach of small businesses. LinkedIn’s fees can be as low as $5 for 1,000 impressions and allow users to set a budget. Advertisers can choose two of seven criteria to target, including geography, industry, seniority, and company size.