Today there are at least 350 social networks. And thousands of smaller, focused and specialized social networks that have been built on Ning — like Etsy, which is now essential for craftspersons, and Architects of a New Dawn, a new age network of “positive and uplifting content” created by musician Carlos Santana.

How do you make your way through this mountain of potential sites and decide where to focus your precious time and marketing dollars?

1. Decide what your market niche is and choose the top 3 networks in that niche.

For example, if you’re a Yoga business, you might want to join the three largest, fastest-growing, or most heavily visited networks in the New Age and Yoga market — Yogamates, Architects of a New Dawn and Gaia. If you are a yoga non profit organization, perhaps you’d also add Wiser Earth. Keep an eye open for all new social nets in your industry and create a basic page on all of them if possible–you really never know where a new customer is going to come from.

The best and most active groups will soon become apparent and then you can start unsubscribing from the less popular ones. (It’s better to have an active page you’re paying attention to than a dead one that could be collecting negative comments or will make your business look stale and outdated.) But in this day of emerging media, it’s difficult to predict in advance who is going to be hot and who’s going to fizzle out. (Once upon a time, only two years ago, Facebook was just a niche network for Ivy league college graduates).

2. Add the Yahoo groups and Meetups in your marketing niche.

Do a search for Yahoo groups relevant to your market, and join the largest ones. These lists become valuable places to announce and promote your events and services. For example, as a Yoga business, we would join all of the Yoga and Vegetarian Yahoo groups, Google Groups and Meetups in our region. Your profile should always list all of your Facebook, Linked In and Twitter profiles, your website, blog and any other urls that relate to your business. This generates links and traffic back to your website.

3. Create a Facebook personal page AND a Facebook fan page. Then create Facebook Event pages for all of your events.

Why multiple Facebook pages? Because you will eventually want to separate your personal life from your busines. Also, fan pages offer the potential to send out news to your whole list with one click — whereas an Event page created from your personal identity requires tediously clicking on every single name in order to invite people. Trust me, you need both.

Again, link back to all of your other social profiles and URLs from your Facebook profiles. More about how to create a kick-butt Facebook fan page in a future article. There are both free and paid Facebook fan pages, depending on the number of friends you have and the features you want.

4. Decide if Twitter, Linked In, Myspace or Flickr are for you. They’re not for everybody.

Twitter is more impersonal than Facebook — I think of Twitter as where I can blast out news to the entire planet in my professional niche. But Facebook where I reach my closest community circle–real people I actually know.  If your business does not need to reach the whole world, Twitter is overkill. For example, a local pet store probably won’t need Twitter, but a distributor of pet products would use it to communicate with stores, pet magazines, customers and fans.

Myspace is in decline, but is still one of the world’s largest social networks, and because it has music player features that Facebook lacks, it’s still essential for musicians, authors, festivals, nightclubs and entertainment venues. Myspace is not trafficked much anymore for other businesses.  More about music promotion, which is a world unto itself, in a future article.

Linked In is essential if you’re a high tech executive and want to link up with your peers and business development contacts — but it’s fairly useless for a massage therapist.

Flickr or Photobucket are great if you’re a professional photographer, or if your collection of photos is somehow relevant to your business, and it will drive traffic to your other sites because these photos are tagged and will show up in web searches.

5. If you’re a local business, you absolutely need to be on Yelp!

Yelp is essential for all local businesses — whether you are a dentist, offer professional services or run a restaurant. You need to actively encourage your friends, family and best customers to write positive reviews on Yelp — because positive reviews will crowd out the negative ones. More about Yelp and review services like Epinions later in a specific article. One of my clients, a mover, says the majority of his business referrals now come from Yelp so he offers a discount to encourage happy customers to write a Yelp review.

6. Local businesses also need to consider local listing services, specific to their niche.

Proactively seek out the free listings first. The ones that are selling ads will seek you out and beg you to spend. Personally, I would hire a competent social media/marketing consultant first and foremost before I paid for any online advertising. For example, if you’re sending out invitations to events, you’ll want to pay for email lists that reach your geographic and business niche, and you may find value in highly targeted Google Ad Words or Facebook ads. For a local restaurant, for example, you’d want to get listed on Bing.com, Restaurants.com, Yelp, Urban spoon, Fodors, Zagat, Dine.com, Citysearch, Boorah and Gayot, plus you’ll need to pay careful attention to Yahoo and Google to make sure you show up on the local search maps.

More about restaurant-specific social media in a future article, as I start to work for a restaurant client and give you some real world examples.

7. Join video listing services, photo sites and podcasting communities, if relevant to your business.

Video communities like You Tube, veoh, Metacafe, Google Video and Current.TV let you host small video clips for free to promote your business or brand. I have a client who is a yoga teacher, for example, who has clips from several of her Yoga DVDs and cooking videos online and considers that an important part of her promotion strategy. Another client, with an Astrology website, uses podcasting networks to promote his online radio show.

7. Listing sites like Digg.com are important too…but you can deal with those later.

I’m going to save this for a separate tutorial, because listing sites like Digg and Delicio.us are a whole other social animal. These sites, which tend to appeal mostly to a younger audience, are where the community “votes” on the importance or relevance of a topic or article. Your blog is like the center of the wheel that is your social promotion strategy. Get started  building your fan base on social sites and the listing services relevant to your business first, and develop a blog that links all of these sites together - before you worry about the listing sites.

The bottom line is — if you’re customers, peers, pundits and fans are there, you need to be on a social network. If they’re not, I’m sure you have better things to do with your time.