I use this in-class exercise after I have taught the students how to construct LGOs using the generator orbital technique. The previous week, they do an in-class exercise on that topic, and this week, they use the LGOs from the previous week to construct MO diagrams.
Given a centrosymmetric molecule, a student should be able to construct its simplified, σ-only MO diagram.
The students work in groups of 2 to 3. Sometimes I match up "weak" and "strong" students and sometimes I let them pick. I haven't really noticed much difference. I circulate and give the students hints, and each group puts its MO diagram up at the chalkboard. If there is time, I have each group go through the construction of the MO diagram, but often I just hit the highlights.