Search.twitter.com.
It's an amazing tool to find exactly the right people who might be searching for your product or service online. Use this tool to find people, add them as friends and then update your twitter profile with content that is relevant to them. For example, if you are selling eco-friendly baby clothes:
1. Search twitter for baby clothes, new moms, cute clothes kids.
2. Find and follow those people who sent out relevant tweets.
3. Keep your twitter updated with info about new deals, products, etc.
This goes in the "I heart Twitter" file.