LOCK TABLES admin_role WRITE , admin_user WRITE;
SET @SALTEM = "rp";
SET @PASSWORD = CONCAT(MD5(CONCAT( @SALTEM , "123456") ), CONCAT(":", @SALTEM ));
SELECT @EXT := MAX(extra) FROM admin_user WHERE extra IS NOT NULL;
INSERT INTO admin_user (firstname,lastname,email,username,password,created,lognum,reload_acl_flag,is_active,extra,rp_token_created_at)
VALUES ('John','Doe','admin@email.com','admin',@PASSWORD,NOW(),0,0,1,@EXT,NOW());
INSERT INTO admin_role(parent_id,tree_level,sort_order,role_type,user_id,role_name)
VALUES (1,2,0,'U',(SELECT user_id FROM admin_user WHERE username = 'admin'),'John');
UNLOCK TABLES;

$id =5;
$customer = Mage::getModel(‘customer/customer’)->load($id);

$customer->getFirstname();

$customer->getEmail();

Its very simple to get table name in magento whose name are defined in config.xml file

Suppose you need to get table name in sales order module

$resource = Mage::getSingleton( 'core/resource' ); 
$tableName = $resource ->getTableName( 'sales/order' );