Also, you may want to start your players in an adventure that you think that they can survive. This will do two things...
1. Give them some experience with the game system and their characters can get some experience in using their skills.
2. The players/characters can become a little over-confident in their ability to face down monsters, then you can turn up the lethality of the game!!
I love the CoC/BRP game system and Lovecraftian monsters. I would begin with an adventure involving ghouls. You could have the players hired to cleanse some old military cemetery of an infestation.
You could have the players encounter a few ghouls in the graveyard itself, and then as they investigate a mortuary on the grounds they could discover an entrance to an underground "city" of ghouls and maybe the funeral home running the cemetery has been burying empty coffins for years, and has instead been feeding the ghouls the fresh corpses. Maybe the funeral home uses the ghouls to conduct crime sprees throughout the city.
Anyways, I personally think ghouls are a fun, creepy monster that can be used in many ways and can be defeated by regular weapons by the players. This will give the players experience in the game and game system, and give them just a bit too much confidence in your next adventure.