Use very specific reference points in your similes

Sarah gasped. The man standing before them was the closest thing to a giant she had ever seen. He was as tall as the birch tree at the bottom of the garden at 64 Kenton Street, Ruislip, West London and as wide as the bonnet of a 1989 Ford Festiva.

‘Explain yourself!’ thundered the giant, his voice as loud as the maximum volume setting on a Sony Trinitron KV-32S42 when tuned to white noise. ‘What are you children doing in my kingdom?’

‘Please, Sir,’ said Sarah, as nervous as Dave Anglesey of New Park Road, Melbourne waiting for his biopsy results at 8:30 on a Wednesday morning, ‘we didn’t mean to trespass, really we didn’t. It’s just that your castle is as strange and fascinating as the first and, to a lesser extent, second seasons of the cult early nineties television drama Twin Peaks, although, it has to be said, it lacks the consistently compelling quality and fractured narrative of that well-loved landmark in television history.’