How can I avoid unnecessary repetition of keywords in SEO writing?

Hello, recently I switched to a local marketing agency in London. I have been a writer and influential before. But this work has a new twist. Here the boss chases me to write content optimized for customers. Now I understand the basic rules about SEO writing. But, how can I avoid unnecessary repetition of keywords in SEO writing? Is there any tool I can use? Or a specific technique?