As WordPress is used for an increasingly varied array of content, users often add extra meta information to posts that should be displayed in a theme. This metadata includes things like post thumbnail URLs, ratings, or even entirely new blocks of content like callouts or something similar.
First, you need to determine the name of the meta information that the user has entered via the Write Post or Write Page interface. As a theme developer, you'll probably want to give some instructions to your users on what custom meta keys are supported. The meta information entry interface looks like the following example to WordPress users:
You can see the meta key field on the left and the Value field on the right. The meta key is generally more important to you as a theme developer, so instruct your users on what to enter there. If they had previously used a meta key, it will appear in a drop-down list as shown in the following:
After you've determined...