An Iron Golem is a very useful creature. Although it will not follow you (unless it's on a lead), it will kill any hostile mobs excluding creepers (unless they have low health). It does NOT suffer from fall damage and can not drown.
Step 1: Gather Materials
You will need:-
4 Iron Blocks (36 Iron Ingots)
1 Pumpkin or Jack o' Lantern (The choice of block does not alter the Golem's appearance)
If you do not know how to craft an Iron Block see next step.
Step 2: Crafting Iron Block
You will need 9 Iron Ingots for each Block, filling the crafting grid.
Step 3: Assemble the Golem (pt. 1)
Place 4 Iron Blocks in a T-shape.
TIP: Do not attempt to make Golems in small areas, or next to walls as they will most likely suffocate and die.
Step 4: Assemble the Golem (pt. 2)
Simply place the Pumpkin or Jack o' Lantern on top of the centre of the T of Iron.
Step 5: Done!
Enjoy living with your new guardian!