Picking your target audience

Every business has to market, advertise, and promote their services or products to a receptive audience to be successful. Notice, I said a "receptive" audience, because it wouldn't be a good advertising plan to promote auto parts on a "new moms" Facebook group, or promote local landscaping services on a national car repair forum.

First, you have to recognize what you sell. Let's just say for instance you sell natural vitamins, but you don't know much about the demographics that are interested in owning them. First, you should check Alexa.com for a site similar to yours. Assuming you sell natural vitamins, let's check out vitaminshoppe.com:
http://www.alexa.com/siteinfo/vitaminshoppe.com

As you can see in the graphic to the right, the majority of shoppers are women, more college educated, and shop from home. From all of these you can get a general idea that these women are either married, have children, or physically active, so this gives a good starting point. Scrolling down you see that 2% of the traffic comes from and "increase testosterone" search, meaning possibly this is the top product keyword for the visitors and likely for the male shoppers. We can also see India sends a great deal of international traffic compared to other countries, so this is the third approach.

From Alexa, here is what we have for vitaminshoppe.com that you can focus on for:
1. Married, or mothers, or active females
2. Men (or possibly women) concerned about low testosterone
3. International traffic from India.

From here, you could search out Facebook for groups or pages related to these areas, and begin posting responses under your page's ID.
Next, take to Twitter and hit the hashtags #low-t, #children's vitamins, #vitamins india, etc. and build your followers. Don't forget, you should have a feed with automatic hash tags enabled through your shopping cart.
From here, write a blog after conducting research on vitamin needs for Indian consumers, mothers, active women, and middle aged me, and begin publishing articles that include coupons to your store.
Last, begin your shopping feeds to the correct shopping sites. Don't just pick shopping.com, Google, or Bing. Target your feeds to your selected groups by checking their Alexa statistics for these highlights.

It's not hard to pick your target audience, just don't forget to attack that audience once you have picked them.