Re "category/tags" query: Open up includes/related-posts.php and replace:
$tags = wp_get_post_tags($post->ID);
if ($tags) {
$tag_ids = "";
foreach ($tags as $tag ) $tag_ids .= $tag->name.",";
$tag_ids = substr_replace($tag_ids ,"",-1);
$tag_ids = str_replace(" ", "-",$tag_ids);
if($tag_ids)
{
$my_query = new WP_Query(array('tag'=>$tag_ids, 'showposts'=>$postcount, 'ignore_sticky_posts'=>1, 'orderby'=>'rand', 'post__not_in' => array( $this_id ) ) );
with:
$categories = get_the_category($post->ID);
$category_ids = '';
foreach ($categories as $category){
$category_ids .= $category->cat_ID;
}
if ($categories) {
if($category_ids)
{
$my_query = new WP_Query(array('cat'=>$category_ids, 'showposts'=>$postcount, 'ignore_sticky_posts'=>1, 'orderby'=>'rand', 'post__not_in' => array( $this_id ) ) );