Shooting your movie
You should already have a shooting schedule. I recommend keeping to it as much as possible as this part of the project is a complete time sink.
Time Management techniques for filming and here are some tips for the set. Make sure to take stills as well of the whole shooting as you will need it for the posters that you will develop later.
Since you'll be doing horror you will probably end up making fake blood.
Don't forget your costumes.
To create the right atmosphere you need to make sure your lighting is right.
Shooting and editing takes longer than most people expect so don't leave this for later in the term. You should start shooting at the start of the term so make sure you have everything prepared before the holidays so you can hit the ground running.
I hope that part of your filming is to get a variety of different angles and shots so your editing can be easier.
Start by picking your editing program. If you don't have one yet I recommend one of these.
You can use sound effects and music from creative commons places or you can make your own music.
If you want to look closer at the history of music in horror movies check out this clip.
A bonus here is a film that uses free special effect sounds and see if you can figure out how they did all their effects.
Closer look has several on horror movies so you should check them out.