Replace the bulb of your porch light with a simple black light bulb. During the fall months, discount stores and grocery stores carry these bulbs for this use. This casts an eerie glow over your deck area during the nighttime hours, and lends to a spooky, haunted effect.
Place a mini fog machine near your doorway. Conceal the machine behind a plant. Paired with the black light, the fog machine creates an even scarier effect.
Hang the pulled cotton material from a spider web kit across your deck railing. Stick the little fake, plastic spiders to the cotton by hooking them into the fluffy stuff. Add pieces around your doorway or on the external walls of your home around the deck.
Embellish the spookiness of your Halloween haunted deck with the appropriate potted plants such as Venus flytraps, sundews and other potted carnivorous flowers.
Place a CD player near your door containing a disc of haunted house sounds. Playing this disc on a repeated loop during the nighttime hours creates your haunted deck and may just give your neighbors the creeps.