How to change field_tags in hook_form_alter? I have the field_tags set to be a select box (not auto-complete). Inside hook_form_alter, how can I change the default value of the field_tags select box? So far, I have:

function autotag_custom_form_alter(&amp;$form, &amp;$form_state, $form_id){

    if($form_id == 'article_node_form'){
      //change default value here
    }

}


But I don't know how to access the field_tags element and then change the default value. Please help! Thanks.
The field_tags element is likely a widget from the Field API. You can surely alter it from a form alter hook, but be aware that it would not be your average Form API element. The Field API adds post-processor, pre-rendered, etc. functions of its own. These functions may expect things you may want to alter.

You can however, change the default value of the field from the configuration interface of your content type (you need to enable the Field UI module for this). You should also be able to select a different widget (ie. a select box) from there.