It's important to have your pumpkin carving pattern ready before you start - you might find some inspiration here on my page by clicking through the various categories and galleries but there's also plenty more ideas online.
To produce something attractive safely you need a little saw, a "pointer" so you can trace a pattern across your pumpkin as you will see in this instructional video - and quite possibly a "drill" so you can bore holes in areas too small to twist a knife. Basic pumpkin carving kits are widely available, and the very keen can buy electric versions.