Techniques like writing with keyword density checks probably does work but when it comes to converting prospects to customers it doesn't work as well as writing good quality and relevant content.
Because of 'internet culture' it is generally more accepted to write with a less formal tone but this does not mean you can write whatever you like. You should write content that syncs with your target audience and your business goals.
Firstly ask yourself 'why do you have a website?' In other words what is its purpose? The most common answer is probably to attract and convert prospects. Whatever your reason is it should be clear and achievable.
The second question is, who is your target audience?
In other words who are the best people to fit your business goals?
To answer this question effectively you need to know what makes your target audience distinct. Everyone is not a target audience because it is impossible to write content that everyone will want to read.
A common practice for clarifying your target audience is to create personas. Personas are a list of traits that as a whole makes it easy to imagine your target audience like they are a small group of people. You can even give your personas names and photos so it is easy to visualise them.
Finally ask yourself how are you going to effectively influence your target audience with your website to achieve your business goals?
This will give you your strategy. This way is more effective than focusing purely on getting high rankings on Google because it will actually convince more people to do business with you. Also search engines are looking for matching up what people search for with good quality, relevant content. Delivering this in the long term will help your rankings more than applying specific techniques or tricks to improve search engine rankings.
On the other hand, search engines are just computers with predefined programming so how do the work?
for good reason search engine companies keep this information to themselves but companies like google do have press releases. A popular marketing education company called smart insights published an article on TF-IDF. This is a mathematical formula that has been used since the 1960's that helps work out the importance of keywords, a solid guess is that search engines have evolved TF-IDF into something more than a simple keyword density algorithm. TF-IDF Stands for "term frequency-inverse document frequency" and the basic formula.
The basic fomula for TF-IDF is:
- IDF(t) = log_e(Total number of documents / Number of documents with term t in it).
A user friendly tutorial on how to use this fomula is at www.tfidf.com
If your interested in knowing the best practices to write search engine friendly content please read this PDF published by Google.