Once you have identified your keywords and phrases, exactly where you place them on the page, and the prominence you give them, makes quite a difference. Always write for your visitor, but also bear in mind what search engines look for (which is ever-changing!).
Example of good keyphrase placement
The page title and H1 heading should be similar if not exactly the same (although the page title could also include the website/company name preceding, or after as well) and include your keyphrase(s). The content should also contain the phrases throughout. H2 and H3 sub-headings should not be identical to the H1 heading, but should also contain the keyphrase(s).
Anywhere between a 4%-10% density for each phrase is recommended – you can check the density of all words and phrases on a page using this tool: http://www.seochat.com/seo-tools/keyword-density/
