"Nothing" except establish strong military presence on two borders of Iran, and also a very strong naval presence in the Persian Gulf.
A simple look at the map would tell you that Bush did one hell of a lot to establish the necessary strategic platforms from which to deal with Iran militarily.
Beyond which, it would be silly to assume that covert activities in Iran were not also being undertaken during that time.
As for the lack of overt agression toward Iran ...well, two wars at a time, please. Bush would never have gotten Congressional backing for a third.