Just check everything! We went through 10 versions of the plans as M kept 'forgetting' to fix errors we pointed out. Anything that is a change from the standard plans is a candidate for a stuff up. Also look for inconsistencies between different views on the plans, do the side elevations and cross sections agree to the floor plans?
There's also lots of fine print on the plans - read it all as there are details covered that are not in the drawings.