To reduce the vast amount of theoretically possible forms, I generally prefer to come up with ‘Climate responsiveness’ as main criteria. Aspects such as wind direction, precipitation, solar exposure, etc. can be a few of the best criteria to justify the form of your structure. The study of the local climate helps to restrict possibilities in the design of open spaces, solid-void ratio, massing, roof types, straight/curved edges, etc. making your design decisions easier.