We have already looked at one aspect of language - in the section on character we saw how you could use short quotes as evidence.
We might want to say that Iago hates Othello. We can then support this view by looking at his language - he says 'I hate the Moor' and he is constantly plotting behind Othello's back, trying to break up his marriage.
Here we are using two ways of providing evidence - words that are directly from the play are put in quotation marks. The second way is to describe what is said in your own words. For example, 'he is plotting against Othello'. It's often good to combine these methods, perhaps quoting just one word from the play. For instance, we can make the point that Othello starts to hate Desdemona, and talks of the 'curse' that comes from marriage.
The one thing you should avoid is using a long quote - many students write out whole chunks of the play and this is just like retelling the story - there is no reason for it and you'll get no marks for it.