Keep this very important rule in mind while your posting away, marketing yourself or your business:
80% of your content should be informational, educational, or entertaining
20% of your content should be specifically about your brand's products or services
There are people out there on Facebook, Twitter, etc, who literally post ONLY about their business. When you are constantly promoting yourself like that, people are just going to tune you out. Most of your content needs to provide value to your followers.
Treat social networking like a cocktail party. You don't go to parties, hand out business cards, talk about yourself then leave, do you? Reach out to people online as you would at a party. Ask questions about THEM. Send a few direct messages on Twitter. Post an interesting article you read on Facebook. Be a resource, not an advertisement.