<?php $customer_email = "customer@example.com";
$customer = Mage::getModel("customer/customer");
$customer->setWebsiteId(Mage::app()->getWebsite()->getId());
//load customer by email id
$customer->loadByEmail($customer_email);
echo $customer->getId(); //get customer id
echo $customer->getFirstName(); //get customer first name
//to find all the available elements.
var_dump($customer->getData());
?>