Should operations such as landings or approaches be logged when acting as pilot monitoring?
The Pilot Monitoring (PM) or Second In Command(SIC) cannot log the approach. FAA has answered this in a 1999 letter:


  You then ask if, for the purposes of maintaining instrument currency, an instrument approach on the above flight flown by the PIC can be logged as an instrument approach by the SIC.  The answer is no.  As the SIC you have not "performed" the approach as contemplated by FAR 61.57(c) because you were not the sole manipulator of the controls during the approach.