[Radek]

Iron Golems need a +3 weapon. The best tactics against Iron and Adamantine Golems is a ranged +3 weapon. Therefore:
Tansheron Bow (without ammo)
Sling of Everard (without ammo)
Rifthome Axe
Azuredge (I've never tried it)
Stay away from the golem, which is hanging somewhere because it is too big, and attack with your ranged +3 weapon. The golem will lose a few HP whenever you hit him. Be patient. The method works perfectly against all Iron and Adamantine Golems until you reach Suldanesellar.

Notes:
1. Never use arrows and bullets! The best arrows and bullests in the game are all +2 so that no arrow or bullet can hit the Iron Golem no matter which bow or sling fires it. (It does not matter that the bow is, for example, +4. The bow gives you +4 bonus to your THAC0 but it still fires, for example, +2 arrows. Such attack is considered an attack with a +2 weapon - not a +4 or even a +6 weapon!) Only Tansheron Bow and Sling of Everard used without ammo are usable against Iron Golems because the phantom arrows (phantom bullets) fired by the bow (sling) are considered +3 (+5).
2. Do not use Gesen's Bow against Iron Golems! The bow attacks in electricity and electricity heals Iron Golems.
3. Arrows or Piercing pretend to be better than +2 but they are not better! Again, they improve your THAC0 but they are still "+2 weapons".