Congrats on your business venture! You're smart to think about marketing and finding your target market online.
The simplest answer--without knowing more about your business and business model--is to find two sets of people online and AUTHENTICALLY engage them:
1. Your target market
2. People who influence your target market (top bloggers, speakers, etc.)
Any target market worth having has both large and small enclaves online. Find these communities, join them and be a resource for them. Listen before you add your opinion to the conversation and join in when it feels right and when you have some helpful advice to offer--don't just hawk your wares.
Additionally, it's not enough to connect with your target market, you need to connect with people your target market respects and listens to as well.
These taste makers will give you quality referrals and talk about your business to your market--all things that will make your social network more attractive in the mind of your market.
Remember: no one cares what you have to say about you, but everyone cares what others say about you.
Lena West is the CEO and Chief Strategist of xynoMedia Technology, a New York-based firm that helps high-growth companies leverage the power of social media, blogs, podcasts and online communities.