You can always outsource this work to a company (check my signature); however, there are tools available that will help you automate some of the social media marketing process like Twollow
Before you go down that route, you should understand the fundamentals of social media marketing and how to make an effective use of it. You also have to consider your business and what products and services you offer as there are some businesses that just won't get a good ROI through social media marketing.
The basic idea behind social media marketing is to establish yourself as a friend and authority on a particular subject by participating in conversations, providing informative/entertaining links and resources, posting great content (through a blog), and then 5-10% of the time plugging a special or offer from your business. If you go out there with only the goal to sell, you'll be seen as annoying and self-serving. There is a zen like approach with social media marketing, you want to go out and assist others and in return business comes your way.
Here are 16 rules to social media marketing
that I think may be a good starting point for you.