Returns first value of WordPress custom field. Runs it though wpautop() if desired. Has option for you to insert text / html before and after the value, allowing you to wrap the value with content.

wp_show_custom_meta.php

<?php

/**
 * Displays the content of a custom field, along with wrapping code or content.
 * @param  string $key    name, or key, of the custom field.
 * @param  string $before what should be shown directly before the custom field value.
 * @param  string $after  what is output directly after the custom field value.
 * @param  boolean $wpautop filters the value through wpautop().
 * @return string         first value of the custom field, prepended by $before, followed by $after.
 */
function s25_do_post_meta( $key, $before, $after, $wpautop ) {
    global $post;

    if ( $wpautop ) :
        $custom_field = wpautop( get_post_meta($post->ID, $key, true), false );
    else :
        $custom_field = get_post_meta($post->ID, $key, true);
    endif;

    if($custom_field) : //if the user set a custom field
        echo $before . $custom_field . $after;
    else : //else, return
        return;
    endif;

}