Common SEO mistakes

What are the common seo mistakes done by SEO persons or the bloggers... :!:

Choosing Wrong keywords
Using Keyword stuffing
Publish duplicate content
Duplicate add meta title & description
Generate low-quality backlinks
H1 not using Heading tags
Using too many keywords
No Mobile optimization
Poor Social Presence
Slow loading pages

One of most common SEO mistakes is the myth that the most backlinks you have for your website the higher your rankings would be. It is actually about the quality of the links than the quantity.

Some common mistakes are following black or gray hat techniques for optimization.