So what I'm basically asking is where do you get your ideas from.
Drugs.
Alcohol.
A string of poor decisions (not always my own).
Wait you're under age so scratch that.
Vitamins.
Milk.
Smart life decisions that lead to healthy living.
All kidding aside, ideas are going to come from all over. The best way to find them is by mining your imagination. Turn off the TV, Interwebs, phone, etc. and let your imagination run wild. You ever have a conversation with a little kid? Those little bastards are full of crazy ideas and wild stories and they have almost no life experience. But they do have a tonne of imagination and no inhabitions so they will spout off whatever crazy thing is in their head.
Try this imagination exercise:
Go outside and pick up a stick.
Start to play. Pretend the stick is something else.
Maybe it is a sword, a gun, a magic wand, a staff. Maybe it is a talking stick or an alien that looks like stick. Maybe it is just a stick and you are crazed hobo who is going to go around delivering street justice with your new best friend Mr. Beat Stick.
Don't be afraid to be silly. Just don't do anything too stupid like run out in front of traffic or anything.
Once you begin to play and have ideas, let them grow. Don't think about the idea, experience the idea. When you are writing be the uninhibited little kid writing down whatever crazy idea pops into your head. Don't worry about good ideas. There won't be any. But when you are done spewing your imagination soaked ideas over your tear stained notebook, you can seperate the bad ideas from those so bad they border on brilliant. Then rewrite those until they become brilliant.
If all else fails, you are in High School, use that to your advantage. Look at how many movies and shows are about dumb ass kids in High School. Take a look at the dumb ass kids around you and write about the drama filled antics that are playing out all around you. I'm sure there are enough love triangles (or love decahedrons if you school was anything like mine...it took flow charts to keep track of had um...nevermind) to Othello look tame. But if you do write about anyone around you make sure to change the names for both legal and social resons.
So the moral of the post is: use your imagination, don't do drugs, and stay in school.
That's about all I got. Other than "you can't force an idea" and "you can't write your way past writers block, you have to live your way around it...or something like that."