The main misconception of many website owners and the authors themselves is that SEO-copywriting is considered something secondary like a real copy. That’s nonsense. If the article is competently optimized, if the keys are written organically, it is a pleasure to read such a text.
Below I will tell you about the basic rules for creating SEO-texts that I use in my work. This is one of the most important stages, so do not miss a single point.
Use natural key queries. Time for some awkward keys like "Saratov's snowmobiles buy cheap" has already passed. The natural keys are now up-to-date. Don’t break the text because of the awkward keys.

Insert the master key into the first paragraph. It is desirable that the main key, by which you optimize the article, has already met in the 1-2-3 sentence. It should be made clear to the search engines that the article is relevant to its title.
It is not necessary to insert each sub-heading for a key query. There is such a doctrine that SEO-copywriting rules require the use of keys in each sub-title. According to my observations, it does even more harm. Of course, 1-2 keys can be inserted, but only if the optimized subtitles are not more than 50% of the total number of subheadings.

Use key queries equally. You should avoid doing it this way: half the text is peppered with keys and the second is as clean as the first snow. Again, be natural, this also relates to the keys position.

Do not use the master keys in neighboring sentences. The use of the key "SEO-text analysis" in the neighboring sentences will damage the material more than it will bring real benefits. Give it a space, do not put them anywhere. Of course you can use loops in neighboring sentences, but the main or even the same keys should be used with extra care. If it looks natural you can easily use them, otherwise please get rid of them. Spammed SEO-text is a reason to sanctions applied from search engines.

Do not be afraid to break the order of words in the query. Try to use all kinds of entries. The article, which uses only direct entries can hardly reach top position in the search results. It is enough only 2-3 repetitions of direct keys; as for the rest, try to choose other types of entries.

Structuring the material. No one reads a complete text, make articles comfortable for the reader.

Forget about the nausea of the SEO text. All these "nausea" calculated on a percentage base, which are widely used by exchanges is believed to be a pure profanity. The article should have keys, but do not overuse them. The article should be interesting. Keys should not bother the reader. If you stick to these rules, the article will bring new results in the search position.
Make large articles. You can not disagree with this, but the fact remains that the search engines like bulk texts more. Especially Google. On my opinion, the reason is quite trivial: large SEO-texts are less common and you can put more keys into it; they open up a wider topic. What is a large SEO article for me? The one that has at least 4 000 characters.
Try to avoid and not use "impassable" keys. Customers often send me a list of keys in the technical enquiry, which cannot be promoted under any case. What are the keys we talk about? For instance, such as "car, auto, automobile, jeep", etc. You will not get into TOP using these keys, everything was already taken by Wikipedia and the giants of the same level. "Family jeep" can be still adjusted, but not the "jeep" key, that’s almost impossible. You should narrow the requirements.

Do not use keys for different pages in one SEO text. Another feature is a desire to insert all requests into one page. For instance, you can see the following requests "Buy a phone, buy a vacuum cleaner, buy a camera." This is not the way to do it. If you write a SEO-text, then write it under one specific target query. One page should have one target request, and nothing else. If you want to use a request for vacuum cleaner please select a separate page.
It's important to remember a very simple thing: SEO-texts under the new Yandex and Google rules are practically free from any clear requirements. One can observe articles in TOP position where the key is used only a couple of times for 3000 characters. Nevertheless, the search engines consider this to be enough.
And, on the contrary, the edited materials with 100% technical uniqueness are found somewhere on the last position. It's all about the quality of the text: if the text is of a high quality it will be succeeded, the search engine will not bother about anything else.

Final optimization
So, we have a ready-made text for promotion, which only needs final editing. If to be more precise, we need to register tags.
I only remind you that without typing Title means a crime before for you and your text. You can forget to write Description, it's not so critical, the search engines will take it from the text, you may not need to register Keywords at all (I'm doing the same, by the way), but Title is an obligatory requirement when creating SEO text.
One of the main mistakes that I have repeatedly met on dozens of websites is the lack of Title. You can find an optimized text for promotion, there are pictures, but the Title says something like "Plant N". "Plant N" Title has the right to exist only when the key you have is also "Plant N". If you are writing about the sale of CNC machines, then Title should be like "CNC machines sale from factory N". Otherwise, it will be useless; this insignificant mistake can bring a negative effect to the whole project. Refer to the article above.
And you last point is to use pictures. It is desirable to find a unique ones. It is very important for the pictures to register the Alt tag. What should I write there? I prescribe an analog of the text from the title in case with one picture, and the main keys from the list, if there are many pictures.
Now our material is ready to work. You now have to place it in the "Original Texts" Yandex Service (before publishing it) just to confirm your authorship. One more step is to send the announcements of the article to the social networks (you can only use the link, do not copy the whole text). And the last but not least: add your text into Addurl Yandex and Addurl Google.
Now you can wait for the first guests. By the way, keep in mind that even if your article is perfect, it’s unlikely that you can reach TOP position soon. Typically, the search engines drive the material upward in several stages. Sometimes it takes a month for a complete cycle, and sometimes it can take a year. So be ready for this.
That’s it, guys. I shared the basic rules of writing SEO-texts that I could, the ones I use in my job. I hope it was useful. If there are additions or questions, I invite you to leave comments.