Below is the list of On page SEO Checklist

On page SEO Checklist

Keyword placement:

Keyword in Title
Keyword in Permalink
Keyword in first paragraph
Keyword in Image Alt tag
Tweaked Keyword in H2 or H3
Bold Important Keywords and related keywords
Italics 1-2 important Keywords
Outbound Link to relevant high-quality sites
Internal links to related articles
Remove all stop words from Permalink
Add multi-media (Video, Slides, Infographic)
Longer the content length, better it is. Minimum: 700 words
Optimize image before uploading (Compress and resize)
Page loading time
Use LSI Keywords (Use Google search to find related Keywords)

Other things:

Use Meta title in less than 65 character
Use Meta description in less than 150 characters.
If using any Social SEO plugin, make sure to add image for Facebook, Twitter. (Take advantage of social graph)
Make sure to have social sharing buttons at the end of post or floating social sharing buttons.
Have related posts after blog posts to lower down bounce rate.

Things not to do:
Not more than 1 H1 tag (Your Post title is H1 tag)
Don’t repeat H2 and H3 Tag
Don’t increase Keyword density by more than 1.25%

Things to focus on:

Try to use Keyword in Post Title at beginning
Use Long tail keywords (You can use up to 65 Character in Post title)
If writing in evergreen niche, remove dates from the posts. (Use Date Exclusion SEO plugin)
Content length: The longer the length of the content, better it is. Though don’t try to uselessly increase the content size.
At the end of blog post, ask users to take action.