I'd recommend you pick up a programming language (if you havent already), and experiment with creating some algo's. You can then run those while you're in school, and tweak / learn as you go. By the time you're done with university, you would hopefully have a working model or two. Frankly speaking, trading these days are less like the desk cowboys you read about, and more coders and statisticians. With the massive amount of data out there, you pretty much need to some kind of automated system to chew through them.
My interest was sparked when I was 12, and that's when I began following the market. I wanted to trade, but I'm glad I waited because I would have lost LOTS of money. If you feel confident enough, start one of those simulated sites for at least a year or two and then see whether or not you want to trade. Also, don't expect to triple your money or increase it exponentially. Aim for a lower goal, like 10% overall, or something higher than a CD rate.
Don't even try. Wait until you actually have a formal education. Most likely, the phrase "Crowding Out" means nothing to you. There are companies you can like as long term investments, but not for fast money. Learning econometrics and empirical analysis should be a primary goal, and will earn you a BS. Do not think your quantitative abilities will be sufficient without these courses, or higher level mathematics. If differential equations doesn't scare you, that is probably how far behind the curve you are compared to someone with even macro and microeconomics. Your investments theory class would be a good start, but independent study other than the CFA Curriculum will not teach you everything you need to know to trade financial markets succesfully. I remember when I was 13 in 1999. Told Dad to buy YHOO at $50 per share. It went to $250 very soon after. Do not expect the same because it is unlikely without top down and bottom up analysis. If you've taken economics, that's a good start, but nothing like what a 4 year college degree will teach you about investing. Wait till you have your education, but, until then, like so many others, you should index passively until you're ready to make stock specific investment decisions.
And the other side of the coin - go ahead and try. Even if it's virtual dollars, you should try and continue to try. Maybe you'll be a quick study, nobody knows, incl this jerkoff saying don't try. Maybe it'll take awhile, but starting young puts time on your side. Anyone that shoots down the pursuits of young people is simply projecting their own failures. Yes, this business and any business w/ unlimited earning potential is tough, but you'll never know unless you try. So if this is what you want to try, then try it! Get a virtual trading account and try! If it gets depleted, try again! And along the way you'll be learning about the markets, how it works, what $ signs look like on the screen and most importantly, if something like this interests you long term. You may try it and hate it. Great! Now you know! But you won't know, unless you try. And if you find it's something you enjoy and have an interest in, then you can start to look at colleges that offer a program that has a trading aspect to it like what I posted here and the other thread Mark referenced.
At the age of 16 your main objective should be getting laid and having as much fun as humanly possible while getting good grades Aim to get yourself a solid education. I would continue studying trading and maintaining it as a hobby while you focus on your main objective. Over the years you will hopefully accumulate experience and knowledge to succeed in the financial markets. One of the things about the markets is that there is a learning curve that is very real. Most never make it and there are no shortcuts, although everyone think they are special. Day trading is not a goal in itself. The main objective in trading should be to make money and there are easier and less time consuming ways to do it than day trading. Swing trading has already been mentioned. Look into that. I should add that I think books are an excellent way to start your education. Just make sure that you start doing some practical work with charts not too far down the road.
This isn't an idle projection. This is experience from someone that started an investment club at 18. Then went through 4 years of college. Then went through 3 years of the CFA Curriculum, became an investment advisor by passing the series 65, and a commodity trading advisor by passing the series 3. If he's all set to compete with people like that then yes, he should, but, realistically, he is not. If you don't want to take advice, he shouldn't have asked for it. There isn't anymore competitive arena to play in than the markets. I'm all for encouraging young people, but not when it comes to learning the knowledge necessary to become successful before they actually have it. <iframe width="425" height="349" src="http://www.youtube.com/embed/cp6LiGKljt0" frameborder="0" allowfullscreen></iframe> 2:38-3:40