To achieve top rankings you need to convince the search engines that you are the most relevent site for the keywords that you are optimising for. There are two main ways to do this, which are on page and off page factors.
On page is about dotting the i's and crossing the t's. This is creating relevent titles, metas, keyword density, strong tagging, site interlinking, creating a site map, uploading robot text files to your site. SEO takes up to 6 months to achieve top rankings. However, it is a very profitable. You can even hire experts from websites like SEOclerks, listingdock etc.