The first writing exercise is - write the first sentence for five different stories. The emphasis is writing a beginning after the action has already started.
1)
Bob noticed the bird tattoo on her wrist as the knife entered his chest.
2)
As the motorcycle reached 85 miles an hour, Clarice prepared for the jump across the canyon.
3)
Even though Florence had been widowed for fifteen years, she still loved coming back to the ocean pier where they first danced and dreamed of changing the world.
4)
The instructions were so simple even he could follow them: give the man the keys to the trailer, take the gym bag full of cash, then return to the hotel room and wait for the phone call.
5)
When the girl first came into the office, Max became convinced this lady had misplaced her medication far more than she had lost her dad.