Almost every thing you need to know about the importance of characters in of mice and men can be see through, for example the way they look,
Lenny ; Lenny is described as mentally retarded through out the book.
You can gather this through how the author said about how he looks and walks, the author said he walks with he’s arms not swing but dragging… Like a bear, and was also dragging he’s feet, he’s build was big with a biggish face, we’re as George (smart) has he’s blanket on he’s back , defined and strong.

You can also know a lot through how they are talked about for example crooks (the stable buck neggro) , as soon as crooks is involved in chapter four it’s starts of crook , the stable buck neggro, which is straight away racist and all the people that read this now know him as a stable buck negro, you also see how curleys wife is awfully treated and yet she says to crook “shutup” this shows dominance and then crook ha nothing to see , he even talks about how he ain’t aloud to play cards with other people,he has to stay by him self and have no friends with him , lonely.