After you draw out your design, a pencil works great for this, you can start carving. I usually start off by cutting the hole in the top, see below.
Here Doug shows the proper technique for cutting the top hole, the hardened steel sword may not be available to everybody, and special care must be taken when using this technique. For yet more detailed info check out the Martha Stewart web site, its loaded with tons of great tips.
Finding the proper angle can be challenging, pay close attention.
Don't forget to save the seeds, wash them up, add a little salt and roast them in the oven till crunchy.
When you are all done, put a candle or some other light source in your pumpkin and enjoy.
In Alaska, you can put your pumpkin outside so it will freeze solid, this way you can enjoy your carvings well into the spring. just remember they are out there in the springtime after it starts to warm up, they are a bit of a mess after they thaw out...