A TIME TO WITHHOLD
In Mary Shelley's Frankenstein, as in so many horror stories and movies, the central horror is mostly kept out of sight. In Part I, Chapter V – the chapter immediately following the animation of the monster – there is no mention of the monster whatsoever. The withholding of the very thing that most greatly interests the reader creates a feeling of urgency and suspense. The amplification of interest by withholding is a technique that can be used in any genre.
Prompt
Isolate the thing (a character, an object, a piece of information, a crucial bit of backstory) that your reader is most yearning to get more of. Give small glimpses of it, spaced out in your text. Withhold any full-on view of this narrative object for as long as possible.