Like what most webmasters would advise to you, keep building quality one-way links!
Have you tried checking out your competitor's sites? See what they are doing, what they've done to achieve that ranking, and what makes their site more important than yours. There are a lot of factors to consider here, what's most important is the content, next is your targeted keywords, how you optimize your targeted keywords, the weight of your inbound links and sometimes the age of a website is given consideration.
Because nobody knows exactly how search engine's algorithm works, better stick o their guidelines
