SEO friendly content is one which can be ranked higher easily by the search engines. Some people especially marketers thnk that excessive usage of related keyword in content helps to rank higher. But this process doesn’t work always.
Remember,

Write your Conent for Readers, Not Search Engines

Tips to write SEO Friendly Content.

1. Usage of headings and sub headings
   In content, there should be proper usage of headings and subheadings. These heading and subheadings should be in hierarchy.
2. Linking to related contents
   If there is related contents about the article you are writing, provide link to them. You can either provide internal link or external links.
3. Article Length Optimization 
   You need to take a goal to write article which is user friendly. Make it simple and attractive. Try to maintain the words in article more than 300 words
4. Wise usage of keywords 
   Make proper usage of keywords in article. Don’t overuse and stuff it.
5. Sharable contents 
   Provide option to share your article via different channels.
6. Usage of paragraphs 
   To make article looks nice, don’t use paragraph. For starting a new paragraph, there should be logical reasoning.
7. Linking previous content
8. Internal Linking
9. Usage of keyword in introduction

Also note that:

1. It is recommended to use a primary keyword on every hundred words.
2. Semantics world can be used in content.
3. Content must be unique.