In a relatively short time, social media has evolved (more like jumped!) from optional and auxiliary to your site, to a given. The question is no longer if you participate, but how? Which path is right for your business? Using these media to your best advantage is what makes it all work.

Here's an overview;

The place a social media 'campaign' fits into your web plan depends (of course!) on your business, and the purpose and function of your website.
Sometimes, it's a natural fit, and some are a little harder to find their place. It is a time requirement, so there should be solid goals and reasonable expectations set.

Let's look at it as 5 components, and how & when they fit together:

1. Your Website  - the Main hub of your online presence.
      Your website should have everything that a perspective clielt/customer would need to know.

Here are the big three social media sites, and how they define themselves.
           They give you a big clue as to how to use them.

2. Blog -

Sharing your expertise, gaining a following who are interested in what you have to say, and developing relationships based on exchange of ideas. It may take a while to get your engines greased on this one, but the 2 things to remember to make this work for you are consistency (2-3 times a week is considered good), and content that people will want to keep coming

Another big advantage of a blog is that it helps your google search ratings, since google pays a lot more attention to sites that are updated often.

3. Facebook -

"Giving people the power to share and make the world more open and connected." from facebook.com 
A social sharing site - connect and re-connect with friends, and more.

4. Twitter -

Twitter is known as a micro-blogging platform. It's another way to have presence.
It's good for sharing information via links and gathering a following of people who appreciate that information. Some of these links could be to your website or blog, but sharing information that you've found in other sources is very good.

5. LinkedIn -

LinkedIn is totally professionally oriented, in tone, visual presentation, and the ways people connect with each other.
This doesn't necessarily mean that that's where you should put your efforts.

Main rule of thumb - Be where your customers/clients are. It's another way to let them know you are there.

Connect on LinkedIn