Halloween is coming up and I am at a loss.

It's not celebrated in Germany and my knowledge about the holiday comes from US television shows, films and HP fanfiction. I know we're supposed to go all over town "Trick-or-Treating", and I have already bought a costume for Missy of Clunn (she's a witch, yay! That's my girl!) but is there anything else to it? Any tips?

We do carve a pumpkin every year, but so far only geometric patterns, no scary faces...