I am glad to see this discussion on the historical validity of Acts. I am working toward a dissertation in Acts and cannot simply dismiss that there is some historical value in Luke's narrative. Granted, my minor is theological hermeneutics so i am constantly asking, "how do we know anything is of historical value?"This is THE question, isn't it? It is a question that we must keep before us every minute as we work through our texts. Skepticism must be second nature. But a working skepticism doesn't mean that we ditch the text as unable to yield any historical information. For me it means that we start with the assumption that the text is not directly relating history - that is, as it is written, it is not telling us how history actually happened. It is a narrative of memory and theology. As skeptics, we begin from the position that the narrative must prove its history to us.
So the real quest is the one of historical hermeneutics, trying to recover elements that are older than the narrative itself, elements that might point us to an earlier time - to an earlier history and an earlier theology. Since communal memory functions to continually update the older traditions to keep them fresh and relevant, we can recover older memories and perhaps even sources by observing how the present author reworks the materials to his liking. Whatever he is reworking, is received tradition that he wishes to revise. This I call for lack of a better term, identification of authorial revision of received tradition. So this is my first step in historical reading.
My second step is reading against the grain, trying to read the narrative against its intended purpose, to see if this reveals anything of merit. Part of this process is identifying anything in the narrative that doesn't support the agenda of the author, anything that conflicts with the narrative's flow or the author's stated theology, anything that doesn't fit the author's contemporary story.
Third, I try to identify the bigger story that the author assumes its audience knows but which we might not know. Other contemporary texts help here because they may contain elements of this bigger picture. Mainly, it amounts to sitting down and mapping the elements in the narrative that are introduced but never explained. Then trying to understand these elements based on our knowledge of other texts from antiquity.
Fourth, I use other contemporary texts as points of comparison. In the case of Acts, we are so lucky to have Paul's letters (and James - yes, I think that James is an early letter from the Jerusalem church). These letters give us comparison points to evaluate what is going on in Acts.