In general, Conjuration school spells are rarely subject to spell resistance, and thus useful against golems and other constructs that have spell immunity or the like--so spells like grease, acid fog, Melf's acid arrow, and sleet storm can usually hamper constructs or even damage them. Other spells that can be used to attack indirectly are also quite handy. Transmute rock to mud followed by its inverse, for example, can be quite effective against any golem if it is on (or under) a natural stone surface. Objects hurled by telekinesis, buff spells that make your allies less vulnerable to the construct's attacks or grant their weapons the qualities needed to attack effectively, summoned monsters to absorb attacks and/or flank the construct--all of these are useful things for a caster to do in such a battle. Things to control the battlefield can also be handy--web, some of the various wall spells, Evard's black tentacles, etc.--can also be helpful, although larger constructs generally have the size and strength to make such barriers less effective than they are against medium-sized creatures.