This next link I'm going to point you towards isn't a tutorial per se, but a fantastic haunted house facade that just shows you what a little know can do to dress your next set. Clicken der link to see the rest. (via Haunt Forum).
Extra tip: a trick I've learned from listening to the bootleg FRIGHT NIGHT commentary tracks is to load each set with layers and layers of stuff for the audience to see. This gives the illusion that the set is far grander that what it really is.