Because 90% of all search clicks occur on the first page of 10 results, it pays handsomely to be a top ranked site, but this position is unobtainable for many who are competing with must larger more established sites.
Ranking for specific keywords with earning potential is the goal for most sites, this proces generally starts with determining the search keyword phrases people are actually entering using a research tool like the Google Keyword Tool: adwords.google.com/select/KeywordTo...
the search: Size 12 Running Shoes has more "commercial intent" than Fitness Exercises because it's the search by someone ready to spend money.
Incorporating valuable keywords in content, perhaps dedicating articles to some popular terms help search ranking they can ho into the page meta title, header and text body.
Some sites get the most traffic from "long tail keywords" like: Running Shoes Gel Soles Size 12Blue that they may have never seen before, having a good volume of general discussions of running shoes improves the chances of coming up for such a long tail search. Those facing much more powerful competition may have to target less popular search phrases that the big sites are ignoring.

There are some 200 factors effecting search ranking, one of the biggest you can have some control ocerare links from other sites that are seen as "popularity votes" by these other sites, creating links for the purposes of search rank manipulation is a common practice but strictly speaking a violation of search engine guidelines and must be some in a way that appears to be a natural occurrence. Not all backlinks are the same, some are 1000 X more powerful than others, links should make sense and should come from a page with relevant content, a link from a fitness discussion to a running shoe catalog makes some sense, linking from a auto repair guide would seem more unnatural. Avoid buying roibot generated spam links by the thousands, you may be warned to remove them for being part of an "Unnatural link pattern" by the search engines. Some keywords an be included in the blue underlined Anchor Text part of a link, doing it too often will raise red flag of suspicion.

* Research desirable target keywords.
* Incorporate the keywords in content.
* Get backlinks to both the inner pages and the home page.
* Use rank tracking tools to monitor the sites SEO progress for each keyword.

This SEO authority has a tutorial series on SEO
www.seomoz.org/beginners-guide-to-s...

Here's a Google "on site SEO" guide
www.google.com/webmasters/docs/sear...