[this comment is from a client with quite a bit of experience and SUCCESS with social media - specifically Facebook]
Social media is very important to any business both local and online. I find Facebook to be the most important and have seen many sales come directly from my Facebook page. However you have to be willing to devote some time in builiding relationships with your fellow Facebookers. I spend about half an hour a day on working on Facebook interacting with people in my feed.
You can have a regular page with "friends" or a fan page with "fans" or both. I have both of them. Post your sales and new items and annoucements on your fan page and develop business contacts with your friends page.
Getting new fans takes a while but after you get over that first few hundred it can grow quickly. There are many "Facebook Follows" out there if you search for them. What this means are that other people will follow you if you follow their page. This will help your fan base grow fast and get you more exposure . When someone follows you it will appear in their stream saying that they "liked" your page. That is your opportununity to get a few more fans because all of their friends will see it.
Seek out pages of the kind of people who would be interested in your products or services and "like" their pages and leave a comment on one of their posts so that they know you were there. Many times they will like you back and you will gain a fan.
I find very little to be happening on Twitter and have stopped devoting much time to it. For awhile I worked at it the same as I did my Facebook pages but I really didn't see any results from it. Other people swear Twitter is the way to go but for me it is not.