Everyone uses different criteria to decide what makes someone a hero.

As for myself, I imagine the person and see if the following apply:

This person has qualities that I admire, that I see as noble.

Reading this person's autobiography would be fun.

I would enjoy having lunch with him or her.

I can consider this person in their totality. They're not perfect, but no aspect of their character disgusts me.

If I turned out like this person, I wouldn't be disappointed