By getting elements added to your site like share and connect buttons, and perhaps including a blog for additional content, you can help increase your social media presence. When looking at accounts you should have, or should consider having, that relate to your site think about setting up a Facebook page (for your business as opposed to personal), a separate Twitter account, maybe a Pinterest account, a LinkedIn company page and you could also make use of a YouTube channel and figure out how to do some guest blog posts.
Now this is a lot of work, there is no doubt about that. And you need to consider that element before you bring all of these outlets into play. What do you realistically have time to maintain? Maintenance is a big part of making social media SEO work for you because all the information must be up to date. If someone goes to your blog from a search result and sees that your last blog posting was from two years ago, they're going to make the assumption that everything about your business is probably out of date and not something they want to explore further.
On the other hand, if you keep that content current - have recent blog posts, tweets, Facebook status posts, Pinterest posts, YouTube video uploads - then that potential customer assumes that your entire business is "with it", current and something they want to be a part of. It really is that important - especially to the younger set. Being current, even "hip", is vitally important when you need to not only service your existing customer base but also grow new branches with every search result.
Ideally, once you open the accounts you decide upon, you should aim for posting a minimum of twice per week - more if you can handle it. You will not want to post just because it's something you have to do though. You need to post content that is useful, or entertaining, or valuable in some way to potential viewers. Make an effort to provide something that others do not. In this way, you will draw business to yourself, sometimes when you aren't really seeing it in the numbers yet. Many viewers become customers after a period of following your content - it's sort of like breaking in a new pair of shoes. You need to walk around in them a little before you decide they're something you want to wear every day.
Once you've created and maintained your chosen social media accounts for a period of time, make sure your site's content is boosted on a regular basis with current articles - the more the merrier. All of this taken together will increase your rankings for SEO.