These are the below give general SEO mistake by seo experts.

1 Keyword stuffing
2 Broken links
3 Copied copy
4 Duplicate content that appears in more than one location
5 Links from non-credible sources
6 Meta keyword tags
7. Avoiding analytics

Always try to keep quality and quantity for SEO of your website.

keyword stuffing and bad backlinks, and duplicate content are the mistake which every one can do.

Following are General SEO Mistakes :
Duplicate Content
Keyword Stuffing
Putting space or dot in your anchor tag