Dave's thin shoulders were stooped, and he wore the plaid jacket that he always wore in the winter. The office was too cold, he thought for the thousandth time. His hair had been less sparse and less gray when he first bounded up these stairs twenty years ago. Today, though, he gripped the rail with one hand, hauling himself up the 24 steps to the second floor. His usual brown lunch sack was clenched in the other hand. "Today," Dave muttered to himself, "I swear something's going to change."
Dave pulled the gun out of his rumpled lunch bag and shot Janice the HR lady through the eye. She squawked once and crumpled heavily across her desk, knocking the open bag of cheese doodles to the grimy carpet. Virulent orange powder drifted lazily down into the spreading pool of blood.*
When I came up with the opening paragraph of my current work in progress, those were the criteria I used to decide whether to start the story there: Does this opening skip the exposition and drop the reader immediately into the story?
Bone Mother was tired. The hut caught a deer in the night, and the doe's shrieks and the crunching of bones kept the old woman awake long after the last of the hot blood seeped into the yard. Years ago, when the world was younger and her heart was, too, she hated the hut, and tried to pry the forest's wanderers out of its ivory-toothed maw. It was never any use. The deer, the rabbits, even the men that slipped through the hut's ragged fence always paid with their lives. She put their skulls on the fence posts, to discourage others.**
*For anyone who found the Dave story compelling, here's the end:
"Good riddance, you witch," he spat. "Now I'll never have to look at another one of your snack-stained expense reports again."