with filters, I just clean them with boiling water and use fresh media. used plastic plants, i soak them in a 5 gal bucket with water and a cap full of bleach, i do another rinse in fresh water then a third soak with fresh water and a dechlorinator like prime. I do the same for tank decorations and rocks. i don't think i'd try that on gravel though.
I have boiled gravel, but you risk removing he coating. I've just been rinsing mine 3x in a bucket with boiling water.