Characters in this novel speak directly with each other, give insinuations, and use gestures.
For example, to illustrate that George and Lennie have gestures that provide meaning to each other, when George was talking to the boss for the first time and Lennie spoke when he wasn't supposed to, the narration reads:
George scowled at him, and Lennie dropped his head in shame at having forgotten.
Gesture also occurs between Curley's wife and all the men as she makes efforts to use her ability to flirt to just earn the friendship of the men.
To demonstrate the use of direct language, George often gives Lennie directions that Lennie is supposed to remember. Lennie is often asked to rehearse these directions:
What you gonna say tomorrow when the boss asks you questions?
I... I ain't gonna ... say a word.
Finally, George insinuates there is a time to come, during which, Lennie will be rewarded for good behaviors. Whenever he needs to communicate to get Lennie to behave in a certain manner, he references "livin off the fatta the lan'" and Lennie chimes in with correct behaviors.