First you cut a hole in the top around the stem. Make sure you do it at an angle so you can put the top back on like a lid.
Next dig out the guts of the pumpkin with a spoon, getting all the seeds and the gooy stuff out first. Then try scraping around the inside of the pumpkin, this will make the walls thiner and the Jack-o-Lantern last longer, but be careful not to make the walls too thin or it will make it more fragile and carving it harder.
Next pick your design. You could try Manny's face as seen in the pic above, or one of the more generic designs might be safer if this is your first. When you cut it to make the holes of your design, try to angle in like you did with the lid. This will give your Jack-o-Lantern more of a orangy glow.
I'd like to celebrate this year, but as always I have a test to prepare for. grrr, one day I'm going to have time to celebrate.