Step 1: Starting Out...

Start by creating a quarter of the pumpkin outline in the top view port with the free form line tool. Utilize control points with F10 and F11 to refine you shape until you are happy with it. Then use the mirror tool to create the second quarter. And then again to complete the 2nd half. Once this is complete join all four parts to create one solid line.

Step 2: Creating the Rail and the Face.

Start the rail in the front view on one of the two quadrants. Use your control points again to get the shape you want. Then create any face you want or find one online that you can copy. I just made one eye and half the mouth and mirrored them just like the 1st step.

Step 3: Make the Pumpkin

Use the rail revolve tool to wrap the vertical curve around your base circle shape. Use the copy and scale tools to create a smaller pumpkin shape inside the first. Cap the planer holes of both shapes to create solids. Make sure the smaller pumpkin shape protrudes through the bottom slightly. Then use the difference tool to remove the smaller shape to create the void in the pumpkin.
Use the extrude tool to make the face curves solids that protrude through the shell.

Step 4: Making a Stem

Start by creating another shape just like the pumpkin base. Then scale and copy it a few times. When this is complete and you are happy with the shapes we are going to set them up to be lofted. Moving and rotating the 4 parts to create the curves for the loft. This is made easier if you create a line that shows the path of the stem you want to make. Now use the loft tool and select all 4 curves in order from largest to smallest and hit enter. Then just cap the planer holes to make the stem a solid. Then all you have to do is move the stem into place and you have your vary own Jack o' Lantern. I used the render mode that is build into Rhino but you could export it into any one you choose. I also like taking my final renders and put them into sketching software so you can add details that you just cannot get is most software.

Step 5: The End...

Hopefully this helps someone out. Also this is my first instructable so if you have any tips for me please leave a comment for me.

Thanks for reading!