Clear Magento Cache
If something breaks, this is the best place to start. Often the reason Magento crashes is due to someone doing something stupid. Stupid in Magento translates to “enabling or disabling extensions without first disabling the compiler”.
sudo /shell php -f compiler.php clear
sudo /shell php -f compiler.php disable
sudo rm -Rf /var/www/magento/var/cache/*
sudo rm -Rf /var/www/magento/var/session/*
Verbose Error Code Display
sudo cp /errors/local.xml.sample /errors/local.xml
chown/chmod
refresh error page in browser
Turn Verbose Error Code Display Off
sudo rm /errors/local.xml
Magento Extension Modules Locate
cd ../app/etc/modules
Magento Extension Modules Activate – Deactivate Magento Modules
sudo vi xyz_module.xml
change