Make a draft.
Trust me.
A draft can be very simple or fairly complex. Basically, you make an outline of what you want to happen in your story.
Do not try to limit your story to chapters. This only makes it harder if it turns out that you need more or less space than
originally planned. Instead, use an outline form and do not assume that that is all you will be having.
Example:
I. Open with Jack drinking milk.
A. Ninjas burst into Jack's house and take his milk.
B. Jack is angry.
1. Jack vows to get revenge.
2. Jack calls his Grandma for advice.
3. Grandma tells Jack to unleash the demons of hell on them
II. Jack goes to library and learns how to conjur demons.
A. Jack practices demon summoning on toaster
1. Problems arise as demons take over toaster and refuse to come out
2. Jack calls an electrician
a. The electrition doesn't know what to do
III. Jack calls the Devil
A. The devil makes a pact with Jack.
B. Devil takes down ninjas
C. Jack spends enternitly in hell baking cookies for the Devil.
....
and so on and so on. Now, you do not have to stick to this original plan if you can not make it work. Perhaps Jack does
get the demons out of the toaster and he mails them via FedEx to the ninjas and they reek havoc. But the point is, making
a first draft is a smart thing to do. If you do not, your story is bound to loose its way, and you will no longer know which
direction to go in. You can make new ones as you go along.
Always keep your old drafts to compare with your new ones. This is just for amusement. You will see your ideas becoming
better and more complex, and will frequently laugh at ideas you had a year ago.