This one is a no-brainer, the Yoast SEO plugin is my top recommended plugin for SEO optimization. There are a million posts online as to why it’s the best… Just go give one of those a read if you need more information.
Yoast offers a premium version of his SEO plugin which does have some valuable additions to the free version. The ability to have more than one keyword (super important) and the ability to manage all your 404 errors and 301 redirects right in the plugin to name a few.
We have done a few tutorials in the past, they are still relevant to a degree but your experience may be slightly different based on the current version of the plugin.