Jennifer Conley, creator of RigBox Reborn for Maya posted a look at creating BlendShape Character heads in Maya, which, if you are new to how rigging BlendShape setups might work in Maya for a character, then this will answer quite a few questions, as it is a point of confusion for most people who are first learning character rigging.
Having personally learned this process the hard way, I decided to make a podcast showing the correct way to go about this task, and show what happens when the steps are done in the wrong order
This is a good look at the entire character head BlendShape workflow, as Jennifer shows some common mistakes and what can happen if the process is created out of order. Jennifer also notes that this tutorial was created for her students, but, is gracious enough to share this information with us al, and that is much appreciated.