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()
{
...
$items['my-path/%'] = array(
'title' => 'TITLE',
'page callback' => 'myCallback', // this can be either `drupal_get_form` or your callback function..
'page arguments' => array(1),
...
);
...
}
and define that callback:
function myCallback($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->type = 'MY_TYPE';
// set other base fields such as author...
$nodeWrapper = entity_metadata_wrapper('node', $node);
$nodeWrapper->field_MYTEXTFIELD->set($data['text_field_data']);
$nodeWrapper->field_TERMFIELD->set($data['term_field_data']);
....
$nodeWrapper->save();
...
// finally return response
}