There are two levels of plot going on in Othello.

 One is the personal plot that unfolds around the relationships between the characters—O thello, Iago, Desdemona, Cassio, Rodrigo, and Emelia.  The other plot is the more public one in which Venice is at war with the Turks.  How do these plots intersect, and do they overlap in terms of some of the main themes of the play?  For instance, don’t overlook the line in Act I, iii, regarding where the Turks are headed in their ships—“or this cannot be, by no assay of reason: 'tis a pageant,to keep us in false gaze.”