Hello,
There are 3 main search engines Google, Yahoo and Bing. Mainly people target Google to get high rankings. But how do they work? What I have learn that they stick on these three rules and they are
Crawl, Index and Rank...
Crawl-- Search engine looks for great websites which have quality content and which is simple made website in HTML with no flash and other types of banners on the website. Software's like Spider do these all work of Crawling.
Index-- After searching good website, they index them with their popularity and reputation.
And after that they RANK each and every website.. Top websites get ranked well due to their quality content and originality.
So follow these and get your website reputation high.