Sometimes, websites can offer promo codes for certain actions such as signing up for a mailing list or making an order for a specific price total. Don't ask users to make an extra effort – automatically apply such coupon codes to the shopping cart.

You can also send users an email notifying them that they've been granted a promo code. Make sure users can copy or apply the coupon directly from the email and are redirected to a page where the code is already applied to their order.