How does Iago manipulate Othello in Act 3?

The timing of events is very important in Act III. Iago anticipates and manipulates the other characters so skilfully that they seem to be acting simultaneously of their own free will and as Iago's puppets. For example, it takes only the slightest prompting on Iago's part to put Othello into the proper frame of mind to be consumed by jealousy. Iago exploits Cassio's discomfort upon seeing Othello by interpreting it as a sign of guilt:
"Cassio, my lord? No, sure I cannot think it That he would steal away so guilty-like,<Tab/><T…