Have you installed Google Analytics?
Have you installed Google Search Console?
Wordpress? Install Yoast SEO
Correct All errors - 404 / 500 errors, duplicate content, missing titles and other technical errors
Checking 302 and 301 redirects (Browseo)
Find Broken links - Xenu
Keyword research using Google Keyword Planner
External Link Building - Whitespark
Internal Link Building
Meta Tag modifications
Optimization of Markup tags including image tags
Synonyms in copy

Check out how heavy your site is - Google Pagespeed Tools and fix with a potential set of tools
- https://wordpress.org/plugins/optimus/
- https://wordpress.org/plugins/autoptimize/
- https://wordpress.org/plugins/cache-enabler/
- https://wordpress.org/plugins/query-strings-remover/

Is your site responsive? Does it render on a mobile device? You can check it with a tool like https://search.google.com/test/mobile-friendly

Have you created an XML sitemap and submitted it to Google and Bing Webmaster Tools? Use XML-Sitemaps.com or the Google XML Sitemaps Wordpress Plugin.

Have you created a Robots.txt file and submitted it to Google and Bing Webmaster Tools?

Have you set up social media accounts on Facebook, Twitter, LinkedIn and Google+?