Well, I have a couple of websites on Google top 10 for competitive keywords for more than one year, and the hardest part is NOT getting your website in the Top 10.
The hardest part is to STAY there.
Here is what I do to stay at the top:
1. I add new pages to my website and get link towards them from authority sites (like Squidoo, EZA, social bookmarking)
2. I make sure to update my pages at least once every 2 months (my money pages, the one I want to rank for)
3. I put a blog on my domain
4. I comment on blogs
Important NOTE: for beginners, I do not make this alone, I outsource most of this.
What are your tips to stay at the top of Google?