Somebody sees something, thinks that it was good/brave/great and fills out a form.
They send the form to the Government department that deals with awards.
The Department rates the act by their standards, what they are I don't know, and then decide what the Hero is awarded with.
Of course the better the report is written the more chance of an Award
If there is a lot of heroes, the lesser acts miss out.
If nobody else has been nominated, you could get a top award for helping an old lady across the road.
It is all in the writing, have a read of the Citations of the next few posts,
and these are the second to lowest awards.