One mistake we usually do is looking out of the window ,if feeling something is wrong.It's an IFR flight ,just to DH ,so looking out will only waste valuable time.
Beside the vey important distance/altitude check and the OM altitude check (which btw should be done as an altitude-position check and not the reverse ,getting you in a situation where you'll wait for the OM and land before it), one could always check the vnav path,the vertical speed ,the gs capture point on the lnav route also, the vertical display on the Boeing is a big plus.Also the egpws will add a lot to safety.