Hi Derek,
I wanted to set my quick account of 'practice' aside from Jim's own account for the reason that, from my understanding, he uses the notion of practice as part of his definition of religion - and I did not really want to get into the evaluation of his theory. But, if one has an account of religion (that does not invoke practice as part of the definition) then I think you can understand practice in the way I outline and its not at all vague. I do, however, think that practice is important to religion - I think it almost ubiquitous that actions flow from religious commitments or that religious commitments are action guiding and so have normative force. A commitment that was not at all action guiding; what would that be?

I think that religion, like art and other complex human phenomenon, is quite hard to define. I don't want to get bogged down with a discussion of essentialism and anti-essentialism, but in the end I think we need 'conceptual clarity' on the point. I mean if we feel that it is important to separate "politics and religion" or if you think that the contemporary "return of religion" is an important issue, then you have to be able to say what it is that is returning or what it is you want to separate from what. That makes the conceptual issue more pressing. I think Geertz' formula is reasonable, although many think it is too liberal, but I think it gets the matter in the ballpark (and no reference to practice or sacrality): Religion is "1) A system of symbols which acts to (2) establish powerful, pervasive, and long lasting moods and motivations in men by (3) formulating conceptions of a general order of existence and (4) clothing these conceptions with such an aura of factuality that (5) the moods and motivations seem uniquely realistic.”  Of course: a) you could question whether all religions are symbolic and so forth; b) its formulaic and so we can pursue matters further or develop a richer account of matters- but I think that there is much to Geertz' way of looking at things. Some people might not like the way this formula situates religion as a product of human activity, but I suppose that such a response needs to formulate some reason as to why we ought to consider it as anything else. 

Philip