Instructions
Look in out-of-the-way or hard-to-reach areas. Many standard cards are located in obscure places, but rarely will they be hidden from view. Exploring all the spaces an area has to offer can often yield several new standard cards each trip.
Defeat as many central processor unit (CPU) players as possible. Many duelists will reward you for beating them by giving you a standard or even rarer card. You can backtrack to an area to battle any opponents you miss, if necessary.
Purchase standard cards from the many shops in the game. Dozens of shops populate the game's various locations. Many shops have a standard card that is exclusive to their store.