Quiet students to me present the largest challenge. I find myself constantly wondering if they are getting the material or if they are just moving along hoping for a C.
One of the ways that I find helpfull in dealing with quite students is to have the class do a daily review of material covered with their bookks closed. I try not to single the quite students out but find myself asking them more probing questions about their understanding of the material covered that day. I find that this helps me to at least make sure they heard and understood what that nights class was about. I find it also usually leads them into asking questions about material they are unsure about.