What makes a hero? That's someone who goes above and beyond what's expected of them, beyond their duty in order to help those in need. Usually at significant risk to their own life. Usually while they're terrified - after all, courage isn't the lack of fear, it's being terrified and doing the job anyway!
I think heroes are made. Their upbringing plants the seeds and then when the situation arises, they act. You see this in folks who will dive into a sinking car to rescue a child or who brave heavy enemy fire to rescue their battle-buddy..
Characteristics?
Courageous - They act, even when afraid.
Decisive - They act when there is need.
Helpful - They desire to help those in desperate need.
Dedication to Selfless Service - They act without concern for their own safety.
Determination to do what is right - They will not stand by and watch the right thing NOT being done.
Hope this helps!