The first clearly ominous sign that occurs is when the children gather at the school and start accumulating stones. The chill of foreboding occurs when, in the middle of discussion of teachers and reprimands, "Bobby Martin had already stuffed his pockets full of stones, and the other boys soon followed his example, ...." There is something unnatural and chilling in the way Bobby "already" had filled his pockets stones in the midst of boy's playful and animated conversation and in how the other boys seem to silently leave off talking and automaton like follow his example. These elements produce an image of unnatural silence and dedication amongst robust boys.
the other boys soon followed his example, selecting the smoothest and roundest stones; Bobby and Harry Jones and Dickie Delacroix ... eventually made a great pile of stones in one corner of the square and guarded it ...
The next ominous sign that, along with the above, foreshadows later conflict is the movement of men to collect in the square. They come in silence and, instead of greeting their children, they survey them. Further, they stand in a group together, apart from the boys and, more pointedly, apart from the collection of stones.
Soon the men began to gather, surveying their own children, ..... They stood together, away from the pile of stones in the corner,
The upcoming conflicts foreshadowed with these ominous signs are (1) the role the stones will later play and (2) the division and alienation that is necessitated within families by the nature of the lottery in which families members must turn against each other in the most fateful of ways:
Bill Hutchinson went over to his wife and forced the slip of paper out of her hand. It had a black spot on it, .... Bill Hutchinson held it up, and there was a stir in the crowd. ... The children had stones already. And someone gave little Davy Hutchinson few pebbles.