Disable Comments in WordPress

If you’re tired of spam, or just find that comments are not appropriate for your site, you may want to disable this WordPress feature entirely.
If you are trying to find a way to remove the “leave a reply” text on your content, disabling comments is also the way to go. If you only want to modify the “leave a reply” text, see this tutorial instead.
Disabling comments for a brand new site is easy enough, but if you have an existing site with published content and comments, you will need to take a few extra steps.