I've always loved the idea of writing a film and I have read several books about how to go about writing a screenplay. I don't feel I'll be a good enough writer to actually write the script until I'm in my twenties, however I've had a few ideas for films, see if you like any of them:
Don't wait until you're 20. Start
right the hell now!!! The sooner you get it on paper the sooner you can go places with it. Even if it's not great the first time, you can edit and change it until it's awesome!
1: There is a huge solar storm, interfering with the electricity on Earth deeming technology useless for years. Once technology is no longer of use, everyone has to rebuild society without it and lots changes with its absence, such as the way people entertain themselves, how we rely on each other, get stuff done and how we find out information. The film would have strong themes of communication and togetherness.
Sounds a lot like the TV show Revolution. Good theme, and it has potential.
2: A homeless man decides he can't take living on the streets any longer so he attempts to turn his life around. He does this using the Big Red Paperclip technique (for anyone who doesn't know, a man named Kyle MacDonald swapped a big red paperclip for a pen, and then for something else and something else until eventually he ended up with a house). The film would be based on that story and the main character based on Kyle MacDonald, only his life would be much worse from the beginning to give him a significant reason to do it in the first place. Obviously MacDonald would need to agree to it etc, but it would be like 127 Hours in that it's based on a real life story only changed somewhat for cinematic purposes.
The best of the 3 ideas, imo. It's a great concept, and it really doesn't have to be long. Remember "The Pursuit of Happyness" was a normal length film, and it covered several years of Chris Gardner's life.
3: A man finds out he is terminally ill and is given a bursary for his treatment. However he decides since he is dying he would rather use that money to go and pursue all of his dreams such as going skydiving and travelling places, etc. The treatment would have kept him alive longer but he would rather complete his bucket list than swallow 20 pills every day.
My least favorite of the 3, which isn't to say it's bad. Just that one of em had to be last. lol. There would need to be a more far reaching theme to it than just "old guy finishing his bucket list" though.