When creating a character, always look for ways to “show" the character—through action, dialogue, thought, or appearance—rather than “tell" about the character. This engages the reader more fully and keeps the focus on the action of the story. In Lou Mathews' short story “Crazy Life," we learn about the narrator, Dulcie, and her boyfriend Chuey's current situation in the first paragraph:

Chuey called me from the jail. He said it was all a big mistake. I said, Sure Chuey, like always, que no? What is it this time, weed or wine? He said it was something different this time. I said, You mean like reds, angel dust, what? Chuey says, No Dulcie, something worse.

Not all stories plummet right to the heart of the matter in the opening sentences. Some are slower in showing the character's unique situation before getting to the crux of what makes this day different than any other. Claire Davis' short story “Labors of the Heart" begins like this:

The remarkable thing in dreams: People say what he never hears in waking. Fat. They say it to his face, not behind his back, or clear of earshot. The word is succulent in their mouths—“faaat"—stretching out like the waist on his sansabelt pants. Nothing derogatory about it, only an unabashed honesty. On these mornings, for a few moments, he wakes feeling curiously relieved.

No matter what your character's back story, you can convey it succinctly while keeping the reader engaged in the moment-to-moment experience of the story.