One of your best bets is to find stocks you want to invest in, then practice buying/selling those stocks on paper ... dont buy anything, just do paper trading. See how well you do. Keep daily tabs by calculating the opening/closing value of your account.
If your stock goes down 10% what do you do, buy more or sell out at a loss? And dont just buy more because it's imaginary money. Look at charts and learn to understand support/resistance levels -- this is probably one of the most important parts of trading, yet no one takes the time to do this besides chart guys. Even if you cant read a chart, you should be able to tell at what price a stock has trouble and/or what price a stock seems to bounce off of.
Another way to practice early on is just by following the money. Hop on momentum trades and see how they play out. When everyone's buying, buy what they're buying ... when they start selling or the buying slows down, start selling.
But always keep in mind, there are multiple forces at work in the market. You're competing against other investors, traders, machines/programs, and institutions ... that's why you'll here me say the stock market is 4-dimensional, there are many more forces at work rather than just people simply buying/selling stocks.
Keep us posted as to how you're doing.