ADirectly edit the core files of Magento with proper commenting.
BMage::registerOverride(‘CoreClassName’,’CoreFunctionName’,’MyClassName’,’MyFunctionname’);
CCopy the original Magento core file to the app/code/local folder and customize that file.
DCreate extended versions of core files in their own folder with extension information. app/code/core/Mage/Cms/Model/Page.php app/code/core/Mage/Cms/Model/Page.1.php App/code/core/Mage/Cms/Model/Page.2.php