How to pre-populate a text field when creating a new node? I am using Drupal 7. I have a Content Type called Request. I have two fields "Manager Name" (type Text) and "Manager Email Address" (type Email). When the user creates a new node of type Request, I want to pre-fill these fields with "Hello World" and "nobody@yahoo.com". Here is what I have tried so far (This is all in mymodule_form_node_form_alter):

$form['field_manager_name']['und']['#default_value'] = "Hello World";
$form['field_manager_name']['und']['#suffix'] = "Enter in the name of your immediate supervisor.";
$form['field_manager_email_address']['und']['#default_value'] = "nobody@yahoo.com";
$form['field_manager_email_address']['und']['#suffix'] = "Enter in the email address of your immediate supervisor.";


The two suffixes are working. When I create a new node of type Request, the suffix text appears under the field name, as expected. But the "default_value" fields are not working. What am I doing wrong?
instead of $form['field_FIELD_NAME']['und']['#default_value'] you should use 
$form['field_FIELD_NAME'][LANGUAGE_NONE][0]['value']['#default_value']
try something like:

$form['field_manager_name'][LANGUAGE_NONE][0]['value']['#default_value'] = 'hello world';
$form['field_manager_email_address'][LANGUAGE_NONE][0]['email']['#default_value'] = "nobody@yahoo.com";