Ah, this is like the Holy Grail of Questions for all non-published writers and published authors.
In a way, it's not age necessarily that matters -- it's your life experiences that matters most. The more you "experience" life, the more ideas you'll have. Take a look at Will. The guy can talk forever.

Like most 16 year olds, you are quite "limited" in regards to life experiences. But then again, consider the movies you've watched and books you've read. Also take into account the story and history of your family and hometown. Pay attention to world events and also to your teachers. They all have stories to tell.
And here's a well-known secret: There is nothing new under the sun.
Originality is basically putting creative twists on established tales/motifs/archetypes/etc. Originality (esp. in scripts/plays) is about creating well-known stories but within unique perspectives. Take what has worked effectively in the past then adding in your creative & unique vision to it.
However, originality is a difficult thing. Just because something is original doesn't necessarily mean that it will be "effective." That's the hard part: Juggling originality and an easily appreciated/digested storyline.
Blofeld posted this in this forum:
<a href="http://chud.nexcess.net/board/ubbhtml/ultimatebb.php?ubb=get_topic;f=67;t=000073" target="_blank">Story is about mastering the art, not second-guessing the marketplace</a>
There's good advice there as well.
As far as coming up with ideas:
Always start small. Do not think epic because the details will bog you down.
To brainstorm ideas, you must think by utilizing the "What-If"-scenarios. This is one brainstorm I came up with our Lumiere's first project:
What if an old, abandoned building develops a soul and suffers from nightmares?
With that, I created 9 stories. Some of them could be a short film treatment since a few of them had lots of dialogue.
The point is, before you embark on a script/play, you must be comfortable enough about its MAIN POINT. What exactly is it that you want to tell a story about? Is it worth telling? Do you WANT to tell it?
Personally, I believe that you should write what you want to tell. Do not think about your audience too much, but rather focus on YOUR script. Unless you want to entertain specifically, then throw out your artistic integrity out the door. But if you want to create an ORIGINAL script, then write it your way.
As far as abandoning your previous scripts: never ever fully abandon them. It could be that it's not their right time to be developed. 1 or 5 or 10 years from now, you may come up with an amazing script for one of your unfinished work. Always keep them close at hand. Hey, if you thought of it, then there's a reason for it. That's just my philosophy.
To conclude:
- Brainstorm; ask "What-If" scenarios
- Avoid epic ideas, just to remain focused
- Must feel strongly about idea
- Feel that you can expand and expound on such an idea
Just my thoughts.
