How to decide what information should I place on the item card?

Imagine you have to design an app that will help users in ordering food from the restaurants. You make an order and go to "My orders" where you can see a list of your orders from different restaurants. You have there 2 cards with some information (restaurant title, price... something else). What research should we make in order to decide what information our users want to see first on the order cards? Interview? Card sorting? Priority sorting?

Imagine also that app's owner said "I know what we should put there! How do I know? I'm an owner, just do it". And you want to get some objective data and present it to him in aim to make a useful app not for owner, but for users.