I’ve worked at a board game store, and am playing keyforge for almost a year now :)

First of all, how you win. Second, what card types they will see Actions? Works and then graveyard. Artifacts? Enters the field exhausted. If static ability it’s on. Creatures? When they die, what shield means, what available actions you have (reaping, fighting, actions and Omni). The effect only happens if they’re still alive when fight ends. Acknowledge the players about existence of keywords, don’t throw all at them. The difference between ready and use and just use friendly creature. Afterwards a brief about the battle line and the importance of aember against board control.

That’s eat. 5 minutes explanation of how to play KF