Simple, but true. A co-worker does a lot of trading and uses E-Trade. I'd be careful not to do a lot of short-term things...yes, you can make a lot of money but you can also lose everything. It becomes a kind of gambling, and people get addicted to it. Best advice is to buy something that has shown stable growth and stick with it for the long-haul. Remember you don't make or lose any money until you sell.
Now is the time to buy good stocks cheap, don't buy cheap stocks. Don't invest more than 20% of your portfolio is risky stocks (like GM/Ford), don't hold on to a stock because you bought it a X price and it's so much lower no, once a stock is down 10% sell it (hardest one to do), use stops and limits,