yehudah

Add a meta box to all posts, pages, custom post types to add the old url you want to redirect from (old url) to the new post. 
You can use redirection plugin here: <a href="https://wordpress.org/plugins/redirection/" rel="ugc">Redirection Plugin.</a> OR The other option is the website htaccess file.
This will help you create redirects while creating or updating your site posts or pages, so you don’t need to update the old and new links when you finish updating your website.
so you don’t need to remember:
<ul>
<li>The new posts or pages url</li>
<li>which post or page I all ready redirected ?</li>
<li>repeat 50% of the process again and so on ….</li>
</ul>

Redirect To WP

This will help you sync redirects while creating or updating your site posts or pages, This will sync to the redirection plugin or htaccess.

faddies

Divert all of the 404 broken pages to your home page. Manage 404 errors, and improve your site. No knowledge of Apache, htaccess or Nginx required.

Redirect 404 Page to Home

Divert all of the 404 broken pages to your home page. Manage 404 errors, and improve your site. No knowledge of Apache, htaccess or Nginx required.

Redirect To WP vs Redirect 404 Page to Home