Selecting the pumpkins you'll carve for your Halloween is very important! You should select pumpkins that are uniformly orange, meaning that are ripe. And try to find pumpkins that have no bruises, or nicks. Care should be taken not to bruise during transport, as this will shorten your pumpkin's life-span.
For standard carving without a stencil, decide if it should be tall and narrow, or more rounded, based on your ideas. If you will be using a stencil to carve your pumpkin, select a pumpkin that is as close to the same shape and size as the pattern you're going to carve. If you find a perfect pumpkin but it's missing it's stem, have no fear! You can still use it! Just carve the bottom out for the opening the same way you would do the top. Then, you just sit your light source on the cleaned bottom piece and sit the pumpkin over it. Have fun!