Use candles or flash lights to illuminate just a little. A little Halloween music in the background wouldn't hurt. The person should look like a scarecrow so the clothes should be extra, extra large so some stuffing can be put in. When the little Halloweeners come visiting, the 'scarecrow' can come to life and deliver the candy. Naturally, a little more than just the front door needs to be decorated.
Candles work wonders.
Black and orange are the best for the season, of course, but any candles, as long as there a lots of them, will be a good atmosphere setter. Use candles in lieu of any other lighting, if possible. If more lights are needed, be sure they are as dimmed as possible. Any other decoration that is done for the season will be enhanced when the lights are dim such as hanging spiders and black netting drooping from the ceiling. Eventually at a party, everyone will need to use the bathroom.