Horror movie advice

I'm in the process of writing a horror movie... I've written a few but I want this one to be really good. My other movies were pretty much thrillers, with a murderer, and were short. They were mainly improv movies also. I've got the plot pretty much done...

for this one.. but does anyone have any tips about how to write dialogue, and how to write a script for the rest of the movie? :]

well base it on like these popular girls have a sleepover and what happens is they get pranked call from this mysterious person and dont belive it and the nest thing you know the door slams out open without anyone there and stuff and evryone thinks it the wind and then a owl came crashing through the window and like evryone got scared and try to get home but on their way home theye get ike different booby traps like a net and all that

if you want more ideas funmail me ( : x

answer some of my questions ;]

that's a good idea.. but I have the plot all sorted out already.. what happens and everything. I just don't know how to write a good script..

Keep it suspenseful and try to steer clear of a d-grade slasher movie :P
We're doing the horror genre in English, to create horror its all about atmosphere.
So that cliche it was a dark and stormy night would work better than it was a clear and sunny summer day. I'm not sure of this is making much sense but keep in mind to keep the whole script on the edge and unpredictable, but no so unpredictable that the audience has no idea whats going on, lol
xx

can you telll us what its based on? x

it's sort of like the movie Shutter... about a photographer who is sent to take pictures of this cemetery and somehow captures a spirit, which invades her home.. and wreaks havoc. it sounds lame but it's more interesting and makes more sense than I can describe.