Next time you eat at Pizza Express, be sure to save the receipt! (Or take a picture of it on your phone, because who actually saves receipts?) Your receipt has a code on it, which you can enter online and complete a super quick survey, and hey presto! Free dough balls! Pizza Express also offers 40% student discount on Mondays and Tuesdays and has all kinds of deals and offers, so you can definitely justify going twice.
