I am tring to add payment method custom column in admin > sales > order
with overriding core file by
Copying
/app/code/core/Mage/Adminhtml/Block/Sales/Order/Grid.php
to
/app/code/local/Mage/Adminhtml/Block/Sales/Order/Grid.php.
with following code
$collection->getSelect()->join('sales_flat_order_payment', 'main_table.entity_id = sales_flat_order_payment.parent_id',array('method'));
in protected function _prepareCollection()
$this->addColumn('method', array(
'header' => Mage::helper('sales')->__('Payment Method'),
'index' => 'method',
));
in protected function _prepareColumns()
with this getting blank column with heading Payment Method like in the image