It is always
'wp_insert_post' immediately after this). In
$_POST['tax_input'] you will find all the terms for all taxonomies associated with the current post.
0 => '0',
To change the terms you have to call
wp_set_post_terms( $post_ID, $tags, $taxonomy ); manually, just changing these values will not work because they are set when the actions fire.
For an existing post that is updated you can hook into
Parameters for all these actions are
$post_ID, $post in this order. For
'post_updated' there is a small change:
$post_ID, $post_after, $post_before.