Add read more button with the_content() function
Its quite simple to add the Read More button with the_content() function, the_content() function is displaying the content of the current post but if its find the tag into the post then its only display the upper content of this tag into the single post. This is how it looks like in the template part.
the_content(
__( 'Continue reading <span class="meta-nav"></span>', 'twentytwelve' )
); …
