Here is a step by step Instructable to make a spooky pumpkin.
Step 1: Find a Pumpkin.
Find a pumpkin with lots of room to draw and carve on.
Step 2: Cut Off the Stem.
Cut off the stem with whatever tools you have available and save it for later.
Step 3: Gut the Pumpkin.
Now cut a hole as small as possible making sure that there is no remainder of the stem. Then gut the pumpkin as best you can, then save the remainders for later if you wish.
Step 4: Draw Your Idea.
With markers or expo markers draw your idea on the pumpkin for cutting later. "expo markers work well as they easily come off the pumpkin."
Step 5: Carve General Design.
Now cut out the eyes and mouth saving the pieces for later use if you wish.
Step 6: Add Details.
Now add all your details to the pumpkin. "We used nails as teeth and staples as scar stitches. Now would be a great time to use all those left over pieces that you have been saving."
Step 7: Let It Burn. "Some Men Just Want to Watch the World Burn."
Now stick whatever can catch fire into the top hole from your pumpkin. Lite it on fire and then watch as it turns into a flaming smoke machine. "use something that is slow burning so it last the whole night."