Against the background of skepticism in the legitimacy of citizen engagement processes on technological and industrial risk issues, this article engages with the methodological and conceptual challenges of engaging citizens from the bottom-up. A public engagement methodology is presented aimed at anticipating the kinds of issues and problem framings that science, technology and industry bring into being. Drawing on two parallel deliberative methods and informed by two empirical social science research projects, design criteria are explicated on context, framing, moderation, sampling, analysis and interpretation. A feature of the methodology lies in the assembly of emergent collectives and identities that are constituted to negotiate endogenously public meanings, concerns and priorities. The potential of such processes is to reconfigure dominant policy narratives and to move the conversation upstream before pathologies of closure and lock-in set in.