If I knew the beans, I wouldn’t spill them. Here are some questions that might be asked of a candidate target:

People: Leadership or military?

Civilian infrastructure, or war making potential?

Essential utility, long lead-time replacement, or status symbol?

More valuable as a hostage to destruction than destroyed?

If the above is the case, can it be nibbled at, to reinforce the threat?

An attritable resource, or a unitary one-off?

Is there a psychological target?  Leadership,  public, or some specific element?

If the psychological target is the leadership, should the physical target be something inconspicuous to the public, thus allowing the leadership to conceal the loss from their base?

Or conversely, embarrass the leadership to their domestic base? Is Iran a candidate for this?

A neat trick:  Retaliation that negates the logic of tit-for-tat.