Common SEO mistakes can be :
1. Choosing the wrong keywords of your business.
2. Not focusing on Meta Tag & Description.
3. Not focusing on Content Marketing.
4. Website slow loading or page that is not mobile friendly.
5. Not doing Off Page SEO.
6. Broken URL with no redirect link.
7. Not submitting your Business on "Google my Business."
8. Not making Consistent change of websites content or fixing small issues.