Okay, in regards with appearance, Othello is gulliable and takes things at fact value. He is an orator and who is also an imaginist, thus he is often fooled when it comes to appearance and when it comes to reality because he fails to see the truth.
Iago is a strategist and ergo, he see's the reality of things, (despite the fact that he's megalomanic with weak motives) . He uses this to his advantage as he manipulates Othello's imagination, making Othello fall for his machinations.
There's a dramatic irony in othello where only the audience can really see the reality of the situations.
Lol, that's all i can come up with, they made us do it this year too for prelims.
Cherio and good luck.