Model-Based Systems Engineering (MBSE) is an emerging paradigm for improving the efficiency and effectiveness of systems engineering through the pervasive use of integrated descriptive representations of the system to capture knowledge about the system for the benefit of all stakeholders. This presentation describes some of the key lessons and recommended best practices that have emerged from several MBSE pilot projects over the past few years, focused primarily on the application of system architecting principles and methods to the planning and execution of pilot implementations of MBSE.