Get a sharpie marker, use a metallic one if the foam is dark. Mark all around the blades, . I extend the blade lines beyond the blades, all the way to the edge of the die. Now you can quickly see if your fabric is placed correctly.
Next, make sure that you don't move the fabric when you put the plastic cutting mat down. Make sure you don't slide the mat if it's not placed correctly. Pick it up, move it, and place it carefully.
Finally, even though you can cut many layers of fabric doesn't mean that you should! I have a Studio cutter and don't cut more than 4 layers at a time.