Trading with fake money is the best way to get a good understanding of it. It uses real-time market data and you buy and sell just like you would with real money, except it's fake. It's not really a "practice" program, so much as it's just using fake money. It's the real thing.

When you do go for it, don't go for high leverage. I made that mistake I ran 1:50 (I think?) and gambled away about $2k over the course of about 6mo. I actually got that up to about $8k at one time, but it slowly dwindled away from there. I think I pulled out with $500 or something left. It's a great feeling to see your money multiplying with leverage, but the same happens when you lose money too.