Ivan, in that case, we need to look at the context. I was going to say that if there’s an if-clause, then it’s probably the conditional. If there’s a reference to another past event that is mentioned first but happened last, it’s probably past perfect. However, those rules don’t really work:
“If he realized the truth he would become scared.” (This an unreal present conditional. It’s true that this could conceivably be a real past conditional (with "would" in the sense of "used to"), but in any case, it’s “would”.)
“He realized that he’d become his father.” (I wrote this thinking it was “had”, but it could conceivably be “would” either as a conditional or as the future in the past.)
The best strategy is to be aware of the *whole* context — not just verbal, but also the entire situation.