how simple do you want it?
the old saying is: 'put some strangers in a house/same room and kill them'

thats pretty high concept 🙂

what i find is a great way of learning how to write and learning how to shoot is to try a make a horror movie that is set during daylight.
you will find yourself trying to find ways to creep out your auidence but without the 'crutch' of darkness.

On thing to consider is what do you have? If you have a chainsaw, ferrari, beater toyota, write that in. If you have access to a mortuary, or a 99 story office building, or baseball statdium, use that (Kevin Smith had access to a video store, Robert Rodriquez to a small Mexican town). Especially search out things you might be able to use that you haven't seen in movies before, as locations or whatever.

And remember the action that happens in a 99 story office building will be very different than what happens in the mortuary or baseball stadium so use the unique stuff in the script.

What you have access to can and should spur your imagination somewhat.

RJSchwarz
San Diego, CA

Another thing to remember is that digital effects which cost vast amounts of money a few years ago are basically free today if you shoot DV or HDV. For example, if you really want to shoot your exteriors on a stormy night with lighting flashing in the sky but end up having to shoot them on an ordinary everyday night (so to speak), it's pretty easy to replace the sky in the shots these days if you know someone with a decent compositing program.