Summarize the following:
Facebook is, by a wide margin, the most popular social media site. They even allow for separate business pages. Add photos of your office and products. Make sure you keep your page updated with new information, and updates.  Keep your posts short, and use pictures whenever possible. People want things to look at, and you'll need to catch their eye as they scroll through their feed.  Be sure to patrol your page for spam and negative comments. LinkedIn is a business networking site, and is a little more professionally-oriented than Facebook. Make an account for your company, and encourage your employees to join. Put as much information as you can into your company's profile, which will help LinkedIn market you to other users. Post updates to what you are doing, and utilize hashtags to generate attention. Track trending topics as well, and utilize any that are similar to your business. To help generate followers, encourage your employees to follow and interact with your company account.  Make sure your handle reflects your business name or what you do. Matching your company website would be best, as it can help customers remember the relationship. Even something as simple as "#deal" or "#sale" (if you have one) for a hashtag can bring in new customers who may not have otherwise been looking for you. Like the others above, these sites provide a space for you and your customers to interact publically. When you create the page, you can control the content, and make sure it reflects your business in a positive light.  Look for sites that best demonstrate your business, and allow you to show off what makes you great, or unique. A photo-sharing site like Instagram or Pinterest is good for companies that produce items, like jewelry, clothing, or any product where a visual would be helpful. Learn about your customers and the kinds of social media they would use in relation to your company. For example, Foursquare and Yelp are good sites for service industries like restaurants, letting customers "check in" (telling their friends they are there) when they visit, and post reviews. Focus on a handful of platforms, rather than as many that you can find. There are many social media sites out there. Checking your various pages regularly can quickly take up too much of your time.  Link your social networks together whenever possible. Visitors to one site should be encouraged to go to another. Include your social network handles on all printed materials as well, encouraging people to go there. You don't want your page to only be advertisements, that will only turn people off. You want to humanize your audience instead of treating them only as customers. Use the page to tell people a little about your field and your interest in it. A good rule of thumb is a 5-3-2 ratio for posting. This breaks down to 5 posts for information related to your audience, 3 non-sales posts related to your audience, and 2 posts not related to your business. You may find interesting local events, or celebrate achievements among your employees.

Summary:
Create a Facebook page.  Create an account on LinkedIn.  Create a Twitter account. Use additional social media networks. Promote yourself along with your business.