<ul>
    <?php
    $post_tags=wp_get_post_tags($post->ID); //如果存在tag标签，列出tag相关文章
    $pos=1;
    $rpls=3;
    $renum=stripslashes(get_option('related_post_num'));   //文章数量
    if($post_tags) {
    foreach($post_tags as $tag) $tag_list[] .= $tag->term_id;
    $args = array(
        'tag__in' => $tag_list,
        'category__not_in' => array(NULL), // 不包括的分类ID,可以把NULL换成分类ID
        'post__not_in' => array($post->ID),
        'showposts' => 0, // 显示相关文章数量
        'caller_get_posts' => 1,
        'orderby' => 'rand'
    );
    query_posts($args);
    if(have_posts()):
    $i==1;
    while (have_posts()&&$pos<=$renum) : the_post(); update_post_caches($posts); ?>
        <li><?php include('m_post.php');?></li>
    <?php $i++; $pos++;endwhile;wp_reset_query();endif; ?>
    <?php } //end of rand by tags ?>

    <?php if($pos<=$renum): //如果tag相关文章少于10篇，那么继续以分类作为相关因素列出相关文章
    $cats = wp_get_post_categories($post->ID);
    if($cats){
    $cat = get_category( $cats[0] );
    $first_cat = $cat->cat_ID;
    $args = array(
        'category__in' => array($first_cat),
        'post__not_in' => array($post->ID),
        'showposts' => 0,
        'caller_get_posts' => 1,
        'orderby' => 'rand'
    );
    query_posts($args);
    if(have_posts()):
    $i==1;
    while (have_posts()&&$pos<=$renum) : the_post(); update_post_caches($posts); ?>
        <li><?php include('m_post.php');?></li>
    <?php $i++; $pos++;endwhile;wp_reset_query();endif; ?>
    <?php } endif; //end of rand by category ?>

    <?php if($pos<=$renum){ //如果上面两种相关都还不够10篇文章，再随机挑几篇凑成10篇 ?>
    <?php query_posts('showposts='.$renum.'&orderby=rand');
    $i==1;
    while(have_posts()&&$pos<=$renum):the_post(); ?>
        <li><?php include('m_post.php');?></li>
    <?php $i++; $pos++;endwhile;wp_reset_query();?>
    <?php } ?>

</ul>

代码中的 m_post.php 就是文章输出格式文件，可自定义