So, what you'll have to do is turn off all the lights, shut the shades, and face del Toro's darkness. When you're all ready, hit the jump and watch the trailer.
There's a nice simplicity to the trailer as they try to pull you just a little bit into that cinematic experience where the lights go out, and the tension and nervousness mounts with every passing moment. Unfortunately, the whispering dude is reminiscent of Gnarl, the flesh-eating ghoulie from Buffy, which might pull Slayer fans out of the moment a little.
Once the clips start flying at lightning speed, too fast to really discern anything but terror and creepiness, it's just a wait for the final moments, where this time the chills seep into the comfort. Next time you yawn and press those toes between the sheets, you might want to get a flashlight and investigate first.