Habermas and Foucault - tag team

I'm wrestling a tag team of heavy weights; Habermas and Foucault. They are fundamental, at least I've made that realisation, that "A-ha!" moment. In terms of methodology, ie the real pragmatics of methodology, I'm still uncertain. Foucaultian discourse analysis? Historical discourse analysis? Ethnographic interviews? All of the above?

From Habermas I'm drawing on three key ideas; communicative vs instrumental rationality, the decline of the public sphere, the "ambivalent potential" of mass communication. Foucault offers some far out methodologies; his archaeology and genealogy. I haven't even got back to Nietzsche yet.....but I think that he too is fundamental through his conceptualisations of the will to power and the origins of morality.