Quoting is very important in your English exam as the quotes are the evidence to the point you are making.  

There isn't a set 'required number' of quotes to use in an essay, but the usual rule is PEC (Point, Evidence, Conclusion). This means if you make a point (eg. Curley's wife wearing a red dress represents the impending danger the characters are about to be in), you must then provide evidence from the text to support your analysis. You should then link the quote back to the point and conlcude just why this relevant to the question and your main argument of the essay. 

To include a quote, it is better and easier to read if you integrate the quotes, meaning it should flow freely in the context of the sentence. For example, "This is proven by Lennie walking 'heavily, dragging his feet a little, way a bear drags his paws' as he shows base animalistic quailities.".

If necessary, you can change the pronouns or tense of certain words in order for it to make sense by placing the new word in square brackets, for example, "This is proven by [his] walking,' as he, '[dragged] his feet a little.". 

Remember, if this is coursework you will need to reference your quotes. Your teacher will inform you which referencing system you are required to use. Usually, however, in a timed, written exam you would not be expected to reference your quotes, but you may be required to memorise the quotes if it is a 'closed book' exam.