Where can a person get a discount code for games sold on Amazon?

Generally when you want a discount code for games sold on Amazon, you will either have to be signed up for their newsletter (with an active account), buy a game and then wait for the newsletter promo. Otherwise you will have to look for games which offer Amazon discount codes as bonus offers for buying the game. Pre-order games often have these codes as bonuses, for example BiOShock Infinite had one.