SEO Task Update List

Mobile Optimization

Mobile Usability

Mobile and Voice-Related Keywords

Accelerated Mobile Pages (AMP)

On-Page Optimization

Head Section Order

Title Tag

Description Tag

Keywords Tag

Heading Tag

Word Count

Call To action

Image and Video optimization 

Structured Data Markup

 Social Markup

URL optimization

Fully Qualified links

Content Freshness

Make Java Script and External CSS

Sitewide Optimization

Contact Information

Testimonial

Privacy Statement

Text Navigation

Sitemaps

Robots. txt files
Linking Strategy
Server Configuration
Static Pages
No SPAM Tactics
Duplicate Content

Webmaster Tools

Web Analytics

Webmaster Tools Accounts

Crawl Errors Report

Manual Penalty Review

Algorithm Updates

Site Speed and Performance

More: http://www.bruceclay.com/blog/seo-checklist/