The attention span of the everyday average customer is thinning. Until you heavily test, then create your own sales funnel, it is very difficult to know the best place to advertise.
Your sales funnel is your method of directing users to follow your online activity from one place to another until they are lead right to the website that sells your product. Your selling site is called your money site.
Of course, that doesn't mean you are actually selling on your site; it just means it's the site that has your actual sales pitch on it. That sales pitch could be your product catalog, or a landing page with a conversion form on it.
Your money site is usually your website. Every other site should be part of your sales funnel and is used to attract new customers and gain their trust. Allegedly Facebook has managed to win over 500 million users, and it's now common place to tell a customer to "become a fan of my Facebook page."
But why do you tell them that exactly?
Facebook was designed as a website for friends. Originally, no selling or soliciting was allowed, making it a no-pressure website where people could easily connect with one another and share their daily lives.
Now Facebook has advertising, and they allow you to solicit on your business page wall. However, those direct solicitations don't generate a lot of money.
So how should you solicit on Facebook and other social sites in order to make money?
The answer is to give your customers (i.e. followers and fans) reasons to click from the social non-selling website to your primary site, but without making a sales pitch.
1. Post a link to a newly posted article on your website. The article can have ads in it, but the link on Facebook attracted attention to the article, not the ads.
2. Run a contest on Facebook to stimulates interest and drive sales. Perhaps have users guess the score of a local high school or college game. Your fans simply post their guesses to your Facebook wall. The Winner gets a $25 gift card. From this you will get at least 1 customer, and several others that at least considered what you sell.
3. Post photos of your new products so people have a reason to click and see full details on your website. The full details include the purchase price.
4. Upload videos to YouTube that explain your products and services. In the description of each, you need to include links back to your main website where people can see more information.
In each instance, don't say things like "Click here to buy" because that won't get the clicks. Instead you have to offer the user more information. They will click further if they are curious for more, and then once they click you should offer another option for them to click for purchase information. You could offer purchase information on that page, but don't make it the primary attention getter.
The one thing you should never lose sight of is that your website is your money site, and needs to be maintained with that thought in mind. Make your sales pitch on your website, and then drive traffic to it from the social networks.