WordPress provides handy way to get all queries and to debug them easily.
To enable queries collecting add the following in your wp-config.php:
define('SAVEQUERIES', true);
Next should be added to your theme footer (wp-content/themes/<your_theme>/footer.php)
<?php echo get_num_queries(); ?> queries in <?php timer_stop(1); ?> seconds.
<?php
if (current_user_can('administrator')){
global $wpdb;
echo "<pre>";
print_r($wpdb->queries);
echo "</pre>";
}
?>
At the end you should be able to get something like:
134 queries in 0.301 seconds.
and a bunch of SQL queries.