Through availability.

In an interview with the former host of AFV, Tom Bergeron, it was revealed that they occasionally used old footage and picked the people who were available to be the finalists.

"Sometimes videos had aired in previous seasons; other times, it was a factor of our taping date and who could make the trip."

Furthermore, the producers choose the finalists.

1. The voting procedure for the Contestant Shows will be as follows, unless otherwise specified:

A. Of the videos included in each Contestant Show, the Producer will select three (3) finalists based on humor and/or uniqueness as determined by Producer in its sole discretion. During the taping of the show, members of the studio audience will vote for their favorite video from among the three (3) finalists and use an electronic voting system (or an alternate voting system, including but not limited to voting by the general public in person, by telephone or over the internet, as determined by Producer). The first, second and third prizes will be awarded based on the number of valid votes cast for each of the three (3) finalists

---

_{AFV Contest Rules - AFV.com}

So, the producers trump almost everything in the choosing of the finalists.