tag related posts

global $post;
$current_post = $post->ID;

$posttags = get_the_tags();
if ($posttags) {
    foreach($posttags as $tag) {
        $tag = $tag->slug;  break;
    }
$args = array(
'post__not_in' => array( $current_post ),
'tag' => $tag,
'posts_per_page' => -1);
query_posts( $args );
    while (have_posts()) : the_post(); ?>
    <p><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></p>
    <?php endwhile;
    wp_reset_query();
}