Irreale Vergangenheit: hätte ... gemacht

To talk about an unreal past (things that did not happen), use hätte or wäre + past participle. This is the Konjunktiv II of the Perfekt, so you choose the auxiliary as you would in the Perfekt. Verbs of movement or change of state (kommen, gehen, fahren, werden), plus sein and bleiben, take wäre. Most other verbs take hätte.

• Wenn ich das gewusst hätte, wäre ich gekommen. (If I had known that, I would have come.)
• Ich wäre gern mitgekommen, aber ich war krank. (I would have liked to come along, but I was ill.)

In the wenn-clause the auxiliary goes to the very end. In the main clause it takes the normal verb slot, straight after the comma when the wenn-clause comes first, and the participle goes to the end. Use this form for regrets and for what would have happened otherwise.