How does Steinbeck present central characters in Of Mice and Men?

It is through the third person narrative where the
characters are presented and revealed.  Steinbeck is our guide through their lives and
we understand the central characters through this style of narration.  The third person
narrative provides us "stage directions" to an extent.  An example of this would be the
first chapter where Lennie imitates George lying down, reflecting to us that there is a
great deal of admiration that he has for George.  Another would be the excitement and
anticipation that Lennie talks about the rabbits.  While the words tell this to us, the
third person narration allows us to understand the full implications of the meaning
behind the words.  The third person narrative style allows the reader to float in and
out of conversations between characters.  This also allows the main charaters to be
presented and fully understood in a way that a narration from one charater might not. 
An example of this would be in chapter 3 when George and Silm are talking about Lennie
and their past experiences in Weed.  George's use of Slim in a "confessional" manner
helps to bring out information about both of them, but also how George sees Slim in the
same way that a penitent would view a priest.  It is through the third person narration
and the ability to move freely to conversations between the characters that more is
understood about the main charaters in the work.