An important choice for any writer, particularly of fiction, is that of ‘narrative mode’, by which I mean the choice of viewpoint and tense. It is rarely make-or-break as you can usually rewrite your story in a different mode, but you don’t want to be doing this after you’ve written a substantial amount, so it makes sense to get it right early on.
The telling of a story involves at least three people, namely the reader, the narrator and the protagonist (or protagonists). However they can be combined. In a first person narrative, for example, the narrator is the protagonist and speaks with the protagonist’s voice, as in “I pick up the gun and point it at the burglar. For a brief moment I wonder whether I should pull the trigger, but then he moves and my instincts take over.”