To determine the generic human, consider the ability being used for the action and imagine someone who is able to use that ability, but not especially well. This person is not trained in this ability or not very experienced but they are also more than able to perform the minimum effect within that ability. For example, if the action was “jump” with the corresponding ability as “Move,” you would need to picture someone who is able to jump but perhaps not that well.
Sometimes it is best to secretly think of an actual person or a fictional character for each ability (e.g. The Matrix’s “Neo” would be a good example of the “Communicate” ability as he was perfectly capable of communication but wasn’t going to charm anyone into giving him information, etc.). The idea of who this generic person is will differ from Narrator to Narrator, which is normal and expected, the important thing is that the generic human makes sense to you and you are consistent with your use of the generic human. It is also advisable to keep your examples of generic humans a secret from your players as it may become an unexpected point of contention.
For example, Tevhra wishes to jump over a waist-high barrier. This is a Move action, which Tevhra has a score of 4.
To determine the target difficulty of the action, the Narrator pictures the “generic human” attempting the action. This particular Narrator pictures Scooby Doo’s “Velma” as the “generic human” for Move-based actions. Velma, while able to move, is not known for her coordination or physical prowess. The Narrator figures that Velma would have a “somewhat-difficult” time jumping the barrier, which translates to a target difficulty of 7. Tevhra’s Lead will now draw 4 cards in an attempt to reveal a 7 or higher.