When writing a blog post you want to have keywords to make google realize you as a real and true blog. That can be hard sometimes. Going on google trends and a keyword database can help you pick the right keywords. Now when you start writing you want to make sure you use the words correctly. Here are some tips on writing a blog for SEO.
1. Keywords should be in the title, meta description, and in the body(intro, conclusion, header).
2. There should be 3-5 keywords for every 500 words.
3. Your primary keyword is not a secondary keyword.
4. Anchor text should be keywords
5. Make sure your content looks like what is popular for the content. Basically, give the people what they want.