Start small.  Build some generic backlinks via directories or comments.  Start a blog and update it maybe 2 – 4 times a month.  Make sure you practice reaching out with your blog to various social media sites or wherever allows you to post about your recently created content.  Continue this practice until it becomes second nature.  You’d be surprised by the amount of traffic you can drive in.  The best thing to do as a startup is to choose keywords that are not incredibly competitive.