i am not sure if this is sound advice, and i'm not an expert, but this is what i think you could do with you starting in yr11 and all:
- research
there's a few parts to this.
first of all, you need to look at the marking guidelines and syllabus requirements. also, reading past major works and reflection statements MAY help. or it may not. you might lose your confidence because they're written so well. just don't let it bother you if you intend to read it. you might gather ideas from other people's work and this is a good way to start too (but i didn't start that way. it really depends on how you want to do it).
then you should look at the conventions of your genre as jhakka said. i am not really into horror, if i'm you i'd do historical fantasy.
with both you need to research not only on what the features of each genre have but also how a short story is written. so alot of research is involved (research = photocopying texts, lol. hehe, partly joking. well, you do need to spend a great deal writing but research is time-consuming too.)
when you're researching about your genre, you should read famous novels/texts written in that genre. that way you've got a good bibliography.
i can't think of others....
- writing/drafting
i think it's important to start writing. if you don't have a clear plot or haven't decided yet, you can experiment and start your drafts. doesn't matter if they're not good, you can still include them in your journal and discuss why you decided not to use them etc. many of my early scenes end up not being included in my final drafts but that's okay.
editing is important! you might hate to come back to what you've written (if you're like me) and rewrite/edit them, but it is needed. also, beware of a monster called the writer's block. you might get them. in such cases, eat them. *munch* my way to overcome it is read, read, read. and tell yourself it's time to get on with it. eventually you'll get on with it (if not the assignments will make you get on with it).
well, i don't know what else i can say, this is my advice to yr11s.
goodluck with your major work!