Ghouls usually hang around graveyards and old crypts. They do have some similarities to zombies, like how they're both peculiar about what they eat. However, Ghouls are smarter than zombies; they can plan and think.
If you stumble upon a ghoul at a graveyard, do not approach it. Don't laugh at it. Do not poke it with a stick. Don't ask it for cigarettes. Just turn around and walk away at a brisk pace, and you just might make it out alive.