The whole point of social media is to be, well, social. Talk to people! Take part in conversations. Answer questions. Respond to big news. Talk about what’s going on in your business. Note: there’s a fine line between being too self-promotional, however. A good rule of thumb is the 80-20 rule: Eighty percent of the time, you should be talking with people about whatever interests them. The other 20 percent of the time, you can promote your products and services. Mileage may vary, depending on your industry or customer base, but this is a good starting point.
Twitter for Small Businesses - 10 Things to Consider