This is a great article posted on another site (who reposted it from another site, who took it from another), but I thought many would enjoy it here. It is The Lazy Man’s Guide for Constructing a Call of the Cthulhu Adventure, written by Sandy Petersen, original author of the Call of Cthulhu.
Loud war-screams shatter the silence of the forest. The party, scrambling quickly over the thick forest floor, are ambushed by savage elves, dropping down from the trees and rock outcroppings. Their hair is cropped into mohawks and their arms are striped with tattoos.
They attack, and scalp unfortunate victims.