I had previously tried out using blend shapes during the summer break so I had a basic understanding of the process. With blend shapes you have to duplicate the master geometry and alter the duplicates by adjusting the vertices. There are many uses for blend shapes, the main one being a deformation, the other use is corrective blend shapes. This is useful to correct certain areas of the geometry, for example when you open your mouth, there are deformations that take place in the cheeks, so by using blend shapes you can put this in place to add more realism. They can also be used to alter any areas that aren't working correctly. You have to make sure that you don't delete the history or freeze the transformations of the duplicates of the geometry, if you do you the blend shapes will revert back to the original place of the master geometry. When selecting the blend shapes, always select them in the order you created them and then the master geometry last. From here you would create the blend shapes and add set driven keys to allow you to animate it.
I will be definitely be using blend shapes when it comes to my character, most likely in the form of expressions, I will have to make a note of all the expressions I want and duplicate the necessary amount of geometry needed.