Writing search engine optimized content five or ten years ago was a lot harder than it is now. Back then you had to think about what search engines liked. Nowadays you just have to write as you would normally. Search engine algorithms have come a long, long way. That's good because search engine results are more relevant than ever - and writing search engine optimized content is easier than ever too.
You're probably wondering why I'm writing about this - everyone knows how to write for SEO, right? Well, apparently not. I've heard a few horror stories from other writers recently about clients presenting them with ten keywords to cram into a 300 word article. In fact, I've experienced it myself once or twice over the past year. Therefore I think it's important to set the record straight and teach you how to write for SEO.
Write How You Would Speak
When I try to explain to people how I write "for SEO", I tell them that I do my best to write as I speak. You'll be hard pressed to find examples of people dropping keywords in their everyday conversations - which is why using the way you speak as a benchmark is kind of handy. Of course there should be differences between the way we speak and write, but in general, the idea is to keep things as natural and free-flowing as possible.
My secret for writing for SEO is simple - I don't write for SEO. I just write about a topic or keyword as I would normally - because by doing that I'll invariably end up using similar words and related phrases. I don't just rattle out 500 words of content using ten keywords - I meticulously research and shape my content so it's as concise as possible, whilst offering as much value to my readers as possible.
Free-flowing, interesting content attracts links and social interaction. Boring, keyword stuffed content doesn't. And the chances are search engines can tell your content is stuffed with keywords - and they won't bother ranking it anyway.
On-page Optimization
Whilst it's clear that I'm not a big fan of keyword stuffing or shoe-horning keywords into content, I do appreciate the fact you'll want to perfect your on-page optimization. That could be through the use of header tags (h1, h2, h3, etc.) or even the inclusion of relevant, outbound links. Remember however that there's such a thing as an "over optimization penalty" - so don't go too crazy, otherwise your efforts could end up inhibiting your ability to rank your site properly.
High quality content + proper on-page optimization is the way to go. Incorporating long lists of keywords into content should be banished to the SEO history books - along with automated tools, buying links and doorway pages.
I fully expect people to pick holes in my post and say that you must write for SEO, and that's absolutely fine. I've abandoned writing for SEO altogether and it has served me well - the reason I no longer write for SEO is because that's what works for me. If you still know a few tricks that fall within Google's webmaster guidelines that help you squeeze above your competitors in the SERPS then that's great, keep doing them!
For me, there is no such thing as "writing for SEO" any more. Sure, focus your article or content around one specific topic or title - but don't try to fill a quota by cramming in X keyword X number of times. More now than ever users expect quality, relevant content that offers value - not keyword stuffed jibberish. Search engines expect the same.