Adding a Taxonomy term in a node via services
I'm not familiar with Services module or drupal's web service (I usually use Symfony for such Services), but I don't think there are any specific rules for such task. 
Assuming there is a callback in your module which receives a data from external resource, e.g.:

function module_menu()
{
  ...

  $items['my-path/%'] = array(
    'title' =&gt; 'TITLE',
    'page callback' =&gt; 'myCallback', // this can be either `drupal_get_form` or your callback function..
    'page arguments' =&gt; array(1),
    ...
  );

  ...
}


and define that callback:

function myCallback($data /* assuming $data is an array, but It can be another type, JSON, XML... */)
{
  if(empty($data)) {
    // some dummy check
    return 'Invalid data';
  }

  $node = entity_get_controller('node');
  $node-&gt;type = 'MY_TYPE';
  // set other base fields such as author...

  $nodeWrapper = entity_metadata_wrapper('node', $node);

  $nodeWrapper-&gt;field_MYTEXTFIELD-&gt;set($data['text_field_data']);
  $nodeWrapper-&gt;field_TERMFIELD-&gt;set($data['term_field_data']);
  ....
  $nodeWrapper-&gt;save();

  ...

  // finally return response
}