Here's How:
If you've already created a carving design, decide on the shape that will best fit your plan. A large, round pumpkin will look great with a chubby smiling pumpkin face, while a tall narrow pumpkin can be made to look spooky and ghost-like.

Decide on the size that will best fit your decorating plan. A porch display might feature a trio of pumpkins -- one large, one medium, and one small. Or, you might want a group of smaller pumpkins to display on a railing, mantle, or window sill.

Be sure to look for pumpkins that are very fresh and firm.
Avoid pumpkins that have bruised or soft areas or cuts or other visible blemishes.

Pumpkins are not just orange any more. They can be any color from light yellow-orange to bright orange, or white and sage green. While color variations are not critical, you may prefer the look of one over another. Be sure to match the color of several pumpkins if they will be displayed as a group.

Smooth skinned pumpkins are generally easier to draw on and carve, though craggy exteriors can also make effective and sinister-looking creations.

Be sure the pumpkin will sit straight on a hard surface? This will be critical if the pumpkin will sit upright. If you decide to cut off the bottom and scrape the seeds out from that opening, a slight tilt can easily be corrected once the bottom is removed.

Place all of the pumpkins you plan to purchase on a flat surface such as a driveway or table to see how they look together and make sure they look the way you want.

Make sure that your pumpkins have at least one good side if you'll display it on a porch or in a window. If it will be used as a centerpiece, choose pumpkins that look good from all angles.

Tips:
You may get the best selection of fresh pumpkins if you shop at a local farm stand.
Buy your pumpkin early and store it in a cool place until you are ready to carve it.