This is the official guide to how businesses can use Twitter to generate business and provide customer service.

"Every company has its own experience on Twitter. But whether a business has been here for a couple of years or just a few months, its twitterers tend to find that certain approaches lead to success. In this section, we share that wisdom, which falls into a couple of big categories."

Here's a link to the full article - 

Best Practices for Businesses on Twitter