It's really hard to answer the question. The methods to use depend upon the shapes you are trying to make. If you are making a very smoothly varying shape, then you might want to add more boundary curves in one or both directions. If you are modelling a hood scoop that changes much more abruptly, then you might want to break the hood up into several different features. It all depends!
First review "Advanced Modeling 301", then "Surface Continuity" to specifically answer your questions. The other presentations listed below will also be helpful for this type of modeling.
remember your surfaces are only as good as your curves. In the Automobile industry the designers layout curves for 2 weeks then drop the surfaces in for two days. Of course they are focused on how light reflects off the surfaces.... A curvature continuity. But if your trying to discuss workflow thats how the auto designers do it. Curves or splines with specific tangency or continuity = specific surfaces that reflect light properly.