[sunshine]

Don't worry about theories like "put[ting] the most keywords of the subject in the first and last lines of the text". They are nonsense. Likewise keyword density and proximity.

Simply create concise, informative copy that contains the keywords you wish to rank for throughout - as they naturally would occur - and your site will benefit.

Tips:
Make sure you place text links throughout your copy to link to other pages using the most beneficial 'anchor text', i.e. use the keyword for the link destination page as your link text (again, as you might naturally).

Use header tags. H1 should be the main subject and contain the main keyword/s, H2 the subheader, and so on. Use CSS to control appearance.

Don't just think about the main keyword but related keywords - make sure you include language which is richly topic-focussed.