Steinbeck presents George and Lennie through the use of dialogue and their actions. Their continuous dialogue, in particular, reveals their highly differing characters, the way that they relate to and depend on one another, and the dream which they share of one day owning their own land. Lennie's simple character is particularly well-emphasized through dialogue, for example the way in which he repeatedly asks George when they're going to get rabbits. George's sharper, more cynical, and yet still caring nature is revealed in his replies to Lennie.
George's essentially caring nature is also presented through his actions, most notably in the way that he always looks out for Lennie. Lennie's childlike nature is revealed through many of his actions, for example his fussing over little animals like mice and puppies. But his unfortunate brute strength, over which he has no control, is also shown when he kills animals by petting them. He also ends up breaking Curley's wife's neck, most unintentionally, when, like a child, he starts patting her lovely soft hair.