Change button name using form_alter

<?php
/**
* Implementation of hook_form_alter().
*
* The function is named modulename_form_alter.
*/
function my_hook_module_form_alter(&$form, $form_state, $form_id) {
// Normally a switch is used because you may want to alter more than
// one form and it is easy to add a new case for each form.
switch ($form_id) {
// This is our form ID.
case 'my_new_form_node_form':
// Our kickin' mods go here.
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Save and add new'),
);
break;
}
}
?>