The hook can be your opening sentence or your first paragraph but whatever you decide, keep the description to a minimum and don’t use passive sentences. For example.
Esme’s eyelids flew open, her body tensed and her arthritic joints twinged as the scraping noise came again from the room above.
Another example. This time for an opening chapter.
Laurence Harford emerged from the building into the cold night air and lit the cigarette hanging from the corner of his mouth. Discarding the match, he exhaled, absently watching the smoke blend with the shadows in the dimly lit lane. Moving slowly toward the stone archway and the street beyond, he stopped when a figure stepped into his path. As their eyes met, Laurence’s heart pumped, a sense of recognition and fear registering in his brain. Beads of sweat broke out across his brow, his cigarette fell to the web flagstones and he lurched from the lane into the deserted street, the sound of uneven footsteps sounding behind.
In this second example something is definitely happening. Who did Laurence see in the laneway, and why did he react as he did?
If you would like to send in examples of your favourite hooks, I'll post them here.