The top professional SEO internet marketing techniques #3 and #4 are keyword phrase placement and keyword density.
Our experience has shown that it is important to include the primary keyword phrase for the site or page attempting to be ranked in the first paragraph of the text copy. The closer to the front of the paragraph or first sentence the keyword phrase is placed, the better the opportunity for higher ranking.
Keyword phrase density is recommended to be 2% -4% compared to the full body test for the page to be ranked. We recommend that the keyword phrase density always stay below 10%. Exceeding 10% can flag certain search engines and get the site listed as using spam. Less than 2% and there will most likely not be enough content to be considered relevant.
We also recommend using the keyword phrase in the second paragraph or text body section.
And do not forget the last paragraph. In some instances we have seen web sites ranked using the keyword in the last paragraph on the page. We do not know of any official statement from any of the search engines involving this, but it does happen from time to time when there is not a significant amount or text for the engine to scan though and index on the particular page.
It is very important to mix the keyword phrases into the body of the page in such a way that it is not overly apparent that they are being used as keywords. The text copy should be informative or descriptive involving the content on the page or links to other pages. Always provide relevant content on the page for the consumer and make sure the text copy reads like an article when using paragraph style layouts. A good rule is that if you do not read it without noticing the keywords then it is generally the right mix of content.