We identify a suite of activities in the development process of Graphical User Interfaces (GUI) and include them as part of an approach to a generic model for the GUI Development Process (GDP). This work contributes with: (1) the identification of common activities of previous GDPs, (2) the definition of an approach to a generic GDP limited to its phases and activities, and (3) the integration of such a generic GDP with any software-system development life cycle (SDLC), illustrated with the Spiral SDLC. We show this work is useful by a) highlighting the advantages of our proposal over other methodologies for GDP in Human-Computer Interaction (HCI), b) showing one example of the integration of the GDP into a SDLC, and c) showing the usefulness of our approach in a case example.