friend of mine uses Yoast SEO for his wordpress sites, I have checked it out its a pretty useful plugin. Unfortunately I dont want to pay for a plugin for wordpress anymore so I have found other plugins to try to do what Yoast does.
First thing sitemaps http://www.arnebrachhold.de/projects/wordpress-plugins/google-xml-sitemaps-generator/
next 301 redirects https://thefoxe.com/products/404-to-301
next images alt tags http://www.prelovac.com/vladimir/wordpress-plugins/seo-friendly-images/
facebook, opengraph twitter, google+ etc http://www.webdados.pt/produtos-e-servicos/internet/desenvolvimento-wordpress/facebook-open-graph-meta-tags-wordpress/
how about the famous backlinks