I wanted to hook `node/add/patient-history` form because I wanted to add ajax in that form.

Before adding Ajax I wanted to **get field names correctly**. So I tried this: 

    function ajaxify_form_patient_history_node_form_alter(&$form, &$form_state, $form_id) {
      $form['field_history_patient_id']['und'][0]['#value'] = "Hello";
      // I also tried 
      $form['field_history_patient_id']['#value'] = "Hello";
    }

They are not working. 

I am not sure if I am taking the field names incorrectly or missing something else.

I found some similar questions on stackexchange but with no answers. 

Any advice/links appreciated very much. Thank you.