SolidWorks is a vast digital toolbox. Just as some engineers are more comfortable using one tool over another, engineers using CAD tend to pick specific feature tools they are most comfortable with. This can pose a problem, as simple extrudes, fillets and cuts limit the amount of geometries you can model. Surface modeling, on the other hand, allows the designer and engineer to create any shape they can think up.
I'd like to discuss four simple surfacing tools today that will dramatically improve your capabilities with SolidWorks.
Surface Extrude - Instead of boss extrude, the surface extrude tool allows you to create an infinitely thin surface from a sketch. Once you have created this base surface you may now move to some of the additional surface tools.
Offset Surface - In product design, especially when dealing with plastic parts, maintaining a nominal thickness is imperative. The offset surface tool allows you to offset almost any surface by a specified amount. Working backward form a solid body and shelling does not always work, whereas the offset surface will likely work in it's place.
Trim Surface - The trim command can be the most finicky, but at the same time, most useful tool. You can trim one surface with another surface, plane or sketch. This allows a user to quickly trim away unwanted surfaces, and move toward a desired surface contour. Once you have trimmed your base contour to your liking you are ready for the final surfacing tool.
Thicken - Essentially the reverse of the shell command, thicken allows you to turn your infinitely thin surface contour into a solid body. If you have not controlled your nominal thickness through offset surface, you can easily set the thickness with this command.
Continue to practice with these tools, and eventually you will find that surface modeling allows you to create geometries you never thought possible in SolidWorks. Good luck!