How are the characters in "The Lottery" shown to be "typical folks?
The twist ending structure of "The Lottery" is one of its strongest features. Until the events start becoming tense (the separation of Tessie from the other villagers, the increasing hostility of the action) it seems that this is an amiable event, perhaps something to do with fair allocation of valuable resources. To increase the disparity between the actual event and the effect intended for the reader at the end, Jackson uses simple language almost in the style of a folksy Mark Twain-type story:
Soon the men began to gather. surveying their own children, speaking of planting and rain, tractors and taxes. They stood together, away from the pile of stones in the corner, and their jokes were quiet and they smiled rather than laughed. The women, wearing faded house dresses and sweaters, came shortly after their menfolk. They greeted one another and exchanged bits of gossip as they went to join their husbands.
(Jackson, "The Lottery," Google Books)
During dialogue, the characters speak with familiarity and jokes (late for the meeting, Tessie says "Wouldn't have me leave m'dishes in the sink, now, would you?") and no mention of the eventual end is made. This establishes the characters in the reader's mind as people rather than props; they are given motivations and simple backstories, such as Old Man Warner's age and continuing participation in the lottery, or how Mr. Summers has no children. In every way, they are simply people living in a farming village; there is only the single, horrifying secret (that to them is not a secret at all) that they share making them, at the end, strange and alien.