Get hold of a good looking suite, perhaps from your local market. It needs to be very dress, if you can get tails so much the better. Paint your fingernails with black polish.Buy some artificial vines and wrap them around your sleeves and fix them in place.
Now for the head piece.You are going to have to find a pumpkin that is bigger than your head. Cut it across the base and scoop out the fruit.Cut an opening for your face. To protect any of the inner wetness from touching your face, insert 2 thicknesses of brown paper and line them with tin foil.
What you need to do is continually adjust until you get the fit right.
Finally you should add make up to create and enhance an evil look.

Pine Crest School student carving a Halloween pumpkin: Fort Lauderdale, Florida