Kevin Gibbons provides some great tips for writing, in particular copy-writing for both search engines and human visitors. Ignore this at your peril!
Search Engines
1) Choose your keywords and phrases and stay conscious of them to ensure they appear whenever naturally possible within the website’s text.
2) Spiders pay more attention to bold and italic words, so when you use such formatting, try to make sure it is a keyword or phrase.
3) They read left to right, so place your keywords as early as possible in the text.
4) Spiders consider headlines and sub headings to be particularly important, so make sure they are as relevant as possible and, if natural and readable, contain your keywords.
Humans
1) Alliteration is good. Humans like alliterative phrasing and looking out for such opportunities allows the writer to concentrate on creating elegant copy rather than just functional words.
2) Use short sentences. The online reader is lazy. To help them read the page more easily, keep sentences short and try to limit paragraphs to just two or three lines.
3) Keep a sense of humour. Unless your pages cover genocide throughout history, there will be opportunities to make the odd joke. Seize these. The more personality you have on your site, the better.
4) Call to action. Your copy does not just exist for the reader to read, you are trying to secure business. While your content should not be one endless pitch, do not be afraid to include a call to action somewhere in it.
External Links (pointing away from your site)
1) If you are a human reading a website, outbound links to sources provide credibility and relevant further information. That makes you happy and gives you a positive impression of the page.
2) Should a search engine spider be looking at your content, outbound links to relevant pages are no problem, it will only get suspicious if you are linking out all the time and to irrelevant places.
This will devalue your site’s importance to the search engines and, of course, too many links can make you look very suspicious.
3) If you want to link to a new pages, make sure a new window opens up. The last thing you want to be doing is directing people away from your site.
I agree with many of them but I would also like to add that an SEO copywriter is no longer limited to writing for spiders and humans and add some keywords and keyword densities in the mix. Today’s SEO copywriter needs to write content that can be voted by the people through social media as well. The bar has been raised for an SEO copywriter in the past 2 years and it’s only raising.