How do you make sure that all your boxes are exactly at the same height, especially when you have a tiled kitchen back splash?Anytime you have tile and a countertop you know that both will (or at least should) be installed level. Since the floor may not be dead on, the best thing to do is to snap a level line along the walls where receptacles are to be installed and locate their height off of that. You also could use one of those new laser gadgets.
This way, if some boxes appear to be at different heights no way is it your fault. Blame it on the cabinet and tile guys!