This is an in-class activity I made for my students in a Junior/Senior-level one-quarter inorganic course. 

Unfortunately it was waaay too long for the 1.5 h class (i gave them about 45 min). I recommend taking this and adapting it to a take-home exercise or homework set, which is probably what I will do this coming year. 

Students used Otterbein to look at various structures, starting with low symmetry, working up to very high symmetry structures. I had them go through the "challenge" so they couldn't see the keys at first, but then go back to check their answers.