Draw traffic to your website using Twitter:

Every time you have a new product, a new services, a special or anything that might be useful for your customers you should communicate that to your followers on Twitter. There's a chance they will click on it and go to your site to read more about it and that generates more traffic to your site.

Follow your brand and products on Twitter:

Twitter has become one of the best tools to see what people think about your brand and products, competitors and keywords related to your business. This allows you to reply to any concerns immediately and really know what is what people is saying about these issues.
You can use Twitter Search (http://search.twitter.com) to find your brand on twitter and subscribe thru RSS Feed to get updates of that search.

Use favorites in Twitter as your Testimonials:

Mark all good comments about your company and products in Twitter as Favorites and then use this as a new source of Testimonials. This is done thru the STAR icon on the top-right of every tweet.

Be the expert and leader on your area:

Use twitter to help other people, send tips, recommendations, and valuable links thru Twitter. This will help improve the credibility and image of the brand and company on twitter.

Use Twitter as a customer service tool:

• Reply to all comments about your company and brand:  Designate a person in your company to check search.twitter.com every day and if there are questions or issues about your products reply to them as soon as possible. This will help keep the image of your company and your customers happy thru good customer service.
• Use twitter to let people know your site or blog is under maintenance or down: This will help communicate this to a lot of people very easily and fast.