Cut off the top of a medium pumpkin, clean the interior and top.
Cut holes in the sides to vent. Use an apple corer: you can place the holes randomly for a mod look, or symmetrically for a more classic design.
Rub your favorite seasonal spices on the inside of the pumpkin top: try cinnamon, nutmeg, or allspice. You can press some cloves or star anise in the top as well, or rub on some fresh vanilla bean. (Don't use vanilla extract—the candle flame may ignite the alcohol.)
Place a beeswax tea light candle in the bottom of the pumpkin. Light and let burn. (And never leave a burning candle unattended!)
Alternatively, you could carve a jack-o-lantern which is what I do.
Presentation: You can use a punpkin maybe 5-6 inches high surrounded with gourds and other fall things like leaves, pine cones, nuts, ect as a mantle centerpiece