Well, there are two ways to consider this...is it what Hamlet says, or how he says it that's more imporant? One is pretty fixed; the other varies with interpretation, direction, and individual performance.
Hmmm....Hamlet's normally posited as a character who restrains his own impulse to act decisively, overintellectuallizing the situation and meditating on it instead of doing something about it. Maybe just find examples of equivocation and rationalization in his language? Places where he overuses metaphor and clouds reality by re-constructing an intellectual screen?
Not an inspired thesis, but it might be a place to start (off the top of my head...).
Of course, this goes back the the ultimate 'Hamlet question' anyhow...might want to avoid that.