Suggestions for DMing horror RPG

[Oneris]

Hang a mirror or a masquerade mask or a portrait in the room the game will be run in a few weeks before the game. Then rig it to smash an appropriately tense moment.

Hide a (quiet) fan somewhere in the room and set it on a timer so it blows papers gently or makes hanging crystals/chains clink at odd intervals.

Partly unscrew a bulb in the bathroom for that fluorescent light flicker

Cover all the furniture with white sheets. Optional: Spray paint a child-sized doll white and hide him among the white furniture.

Leave a creepy prop covered with a white sheet under the table where the food is. Someone is guaranteed to look underneath. Note: the food might not survive the ensuing scare.

If you have the time, take white taper candles and burn them down a bit, and while the wax is still soft, jam a piece of red crayon right next to the wick and cover it with more wax. When the flame starts to melt the crayon, it'll look as if it's bleeding.