You just need to full concentrate on that keyword, and join some forums which allow dofollow signatures make as much sig possible. Do some article writing in high pr blogs or article directories respectively.
In this stage the quality of backlinks built will make a lot of difference. It is important to be consistent in terms of building authoritative backlinks. Also, over optimizing the keywords will have a negative impact on search engine optimization, therefore using keyword variations is important.
I agree with the previous answer. You have to analyze your competitors, see what backlinks they have, the sites from which they come. You should try to get focus on getting backlinks that have better quality than those on the competitors. If they have thousands of backlinks of low quality, you can beat them with fewer backlinks of good quality. Use ahrefs.com , even the free version can help you to have an idea on the competitors. If someone knows other sites like it, please share.
Do social bookmarking, and focus on content.