Once people figured out the ranking at the top in the search engines was desirable, good ol' capitalism took over and competition grew. People have used the most creative methods imaginable to give the impression that their sites was more important than it actually is.
SEO "NO NOS"
Below is a list of some of the most egregious SEO "no no's" you want to stay away from.
Don't use the same wording on your pages and definitely don't copy content from other sites.
Including keywords into your site in an unnatural way hurts your users user experience and also hurts your rankings.
Getting links from sources which have little to do with your niche can get your site penalized
Slow Site Speed
Having a slow website harms the user experience and Google and other search engines have factored this into their algorithms.
Content Thin Pages
For Google and other search engines to view your site as a destination worthy of ranking, you must have content on your pages.