How did President Carter's foreign policy approach differ from that of Nixon and Ford? Also...which do you believe was more effective? why?

The main difference between President Carter's foreign policy and the policies of Presidents Nixon and Ford was that Carter's foreign policy was based more on idealism and less on force/self-interest than the policies the other two pursued.

Perhaps the most famous example of Carter's more idealistic foreign policy was his decision to make a treaty giving the Panama Canal Zone "back" to Panama.  There was no need for the US to do this, and you can argue that it makes us less secure, but it seems more like the right thing to do.

It is hard to say if Carter was more or less effective.  Nixon's policies were not able to win the Vietnam War, but they were able to make better relations with Red China.  Carter's policies managed to get the Camp David Accords made, but were unable to prevent the Iran Hostage Crisis.