First, let me start by saying that social media can't replace face to face and in person customer service.
Social media provides a listening tool, if you know what you are listening for. It's almost an expectation of your customers now.
1. Page comments and likes: First and foremost, seeing how your audience responds to what you post is an excellent tool for listening. Whether they 'like' posts about new product, tips or motivational messages, all of these can give you insight into the audience that is viewing and what they like.
As a shop owner, this can help you structure and revise your buying of products (ie: if your customers love black, buy more, if they get excited for patterns, adjust)
As a service, you can gain insight into what your audience appreciates, from tips to events to seeing the results of hour work.
2. Messages and DM's: No I am not talking about that Prince in some far away land that needs your help, Im talking about those 'FYI, my soup was cold' or 'Hey do you know anything about photography' these are tools and tidbits of information that you can use to find out if you need to adjust your staffing, expand your skills or align yourself with others that can help you (subcontractors, software etc). While they may be directly or indirectly related to you, they can be used as a tool.
3. Listening to the landscape: There is a lot of noise in the land of social media, from tweets to shares, likes to videos, but if you stop and read, note trends, common topics, you can use that to your advantage. Here's an example: if there is crime on the rise in an area, publish safety posts, tips about home security (online and off). If everyone is talking about eating laundry pods, its the perfect time to announce you have a new menu, and something far better to eat. Check out what is trending, what people are looking for and, if you can, provide a solution.
4. Join the groups, and the conversation: Whether LinkedIn, Twitter or Facebook, join in the conversation. Many industry groups offer insight into what they see, what is being forecasted and what issues are arising, this is how you can edge out the rest and be on top of it early, from design trends to consumer goods, you'll find a lot of resources. This further helps your beat your competition and provide the solution or desire first for your competition.