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You are likely to choose pages, topics, and themes from your research and with input from search data, but you need to write for your (human!) readers

Some of the best material I have seen on this subject recently is from Kameron Jenkins - for example, check out her SearchLove Boston presentation. She covers a bunch of tools and tips for effective writing. She emphasises the point but from the discussions in the rest of the thread I wanted to emphasise as well, keyword density has never been a ranking factor, and especially these days, the quality of content is paramount. You are likely to choose pages, topics, and themes from your research and with input from search data, but you need to write for your (human!) readers.

Good luck!

If you have Wordpress as CMS, the Yoast plugin is perfect for that. It indicates when you used a keyword really too much or really not enough.

But to be honest, I wouldn't pin myself down too much on using certain keywords a certain amount of times. Keyword density is an old concept, and nowadays it is far more important to write relevant and complete content. Of course keywords are still important (because you have to know what people are looking for when writing your content), but don't force them in.  just use them in a natural way. If you have a great text about a certain topic, this should come automatically.

Hi,

Next to the common tools (SEMRush, Moz KE, Google KWP), there are a few extra (free) options like yoast.com/suggest and www.wordstream.com/keywords. They'll give you some extra long tail keywords that you mostly don't get with other tools.

A little bit more time consuming, is using quora.com. In this great article is explained how to use this forum website to get ideas for keywords by checking (related) questions about a certain topic. Next to the questions you find on Quora, you can copy-paste those questions in the Google KWP to find related long tail keywords and their search volume.

When it comes down to syntax and using exact keyword combinations, it is critical that you write content that is readable. Write for your visitor and not for Google. Of course you need to base your content on keyword research in order to be found as much as possible, but don't force certain keyword combinations into your text when they don't fit in there. Often you see people (even 'SEO copywriters') writing content and combining all of the possible keyword combinations they found, what makes their content look 'forced' in the end. Just write good and complete content based on keyword research, but don't focus too much on using that keyword 7 times, and that long tail keyword 5 times. If you write good and complete content, those keyword combinations will appear automatically in the text, or at least you don't have to force them in.

Hope that helps.