Here is a list of 10 "Commonly Overlooked Best Practices in Social Media" which covers a lot of the simple social niceties that both individuals and institutions should abide by online - things like being kind, respectful, and patient. This includes reading comments people leave and responding where appropriate.
It is also important to keep your profile and blog information up to date. This shows you care about how others see you online, and value any customers that seek information in this manner. Keeping posts relevant ensures your followers that you are reliable and professional.