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:
Redirection Plugin. 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:
- The new posts or pages url
- which post or page I all ready redirected ?
- repeat 50% of the process again and so on ....