You can open an account at ScotTrade for free, and then buy a few index funds that you like. You could either put these into mutual funds, like Vanguard's VFINX US S&P fund, or buy exchange-traded funds which track indices as well.
Investing early is wise, the key thing is not to try to beat the markets (at least not with YOUR money on the line!) and also note that volatility will make you unhappy if you check often. You'll be up and down but, over the long term, hopefully up. But if you check frequently, the "down" times will make you unhappier than the happy-times will make you happy. So, set it and forget it, if you take a diversified and relatively low-risk approach.
For 15k, you could invest across bonds, US stocks, international stocks, emerging markets, and more, all without significant cost or overhead -- if you play the broader markets, instead of trying to pick winners.
Most importantly, keep educating yourself, and not just what other people say on random internet forums ;)
(Of course, tonight I'm the one tempted to make such a suggestion. :-/)
If you're looking for 12-15% a year, you'll have to be doing some very risky stuff. Returns like that are hard to come by. Let me know if you find anything though ;)
%12-%15 is not that hard to get, and doesn't involve substantial risk, but does involve doing your homework.
I would recommend one of Timothy Vick's books on Buffett for some advice.
Back when I was in the equities markets, I was able to predict the return I would get from a stock, buy it, and then, on average, exceed that return. Stocks are not gambling when you buy low, pre-calculate expected return over 5-10 years, and only buy when you are getting a good deal based on the expected return.
I'm out of the equities market because the US dollar is in serious danger, and I would not recommend bonds for this very same reason. I've been doing better in precious metals than I did in equities. But if I were in equities I'd also research some of the good precious metals companies-- some are very well run, and have both equity and growth appreciation by moving assets from discovery to production, as well as leverage to the decline in paper currencies which will cause their resources to have a larger market value. It is one thing to buy gold in the ground for $20 an ounce, it is quite another when gold is going up in price while you're doing it. But this sector takes more research.
IF you're willing to put in some time, it isn't that hard, but first I would recommend learning. The vick book, or Mary Buffetts "buffetology" are good resources. Find people who cover the sectors that interest you, learn all you can, and only invest in your circle of competance.
If you're married it would be best to have your spouse anonymize the companies by copying down the key figures from the annual reports, and then the price on Jan 30th, for each of the next 5 years. Have her keep the company key seperate.
Analyze them on that basis, then look into the prices on the stock market in January 2005. Use those prices and discounted cash flow analysis to predict what their prices will be in 2010. Invest a fake $150,000 in the companies based on those calculations.
Then wait a week. Each week, look up the prices for the companeis a year later and decide if your thesis still stands. For this example, lets just pretend like you have no access to news, no annual reports for 2005, just the price on Jan 30th, 2006. Decide to re-allocate if you want, but pay $100 for each transaction (sales and buys). IF you're down and you sell then you're locking in that loss.
Do this for the next 5 weeks until you've covered the time period to Jan 30th 2010.... and then look to see how your companies did.
Try to draw your conclusions before you connect the fake companies names with the real companies.
Don't forget to account for dividends in the interim as well.
This can be very instructive-- but be sure to learn about how DCF and current trading price affect risk. IF one of the companies did poorly, was it because of bad management? An externality that was unpredictable? etc.