New traders especially should trade small lots, 100-300 shares. Keeps your risks down while getting your feet wet. For that reason a flat-rate broker can add up quickly. I use Interactive Brokers (
www.interactivebrokers.com) which charges 1c per share up to 500, 1/2-cent there after. You can roundtrip 200 shares on a daytrade for 4 bucks, market or limit. Datek for example would be 20.00.
IB is also a super broker in its own right.
In case we are in the beginnings of an intermediate-term rally, don't get too cocky if you do well in the beginning. I started last year, right at the March-April lows and thought "anyone can make money in the market! Piece of cake." Almost each morning I woke up to "Nasdaq futures are limit up".
Then the rally ended and the market kicked my ass bloody. Started with a 7500 account (PDT rules weren't in effect back then). After making 8 grand initially then losing that plus another couple grand or so, I decided to sit down and learn how to trade properly. Who is it that said "Don't ever confuse a bull market with brilliance" knew what they hell they were talking about.
You need to develop a trading plan that fits your style of trading and your capital.
Good luck - this is the hardest job you'll ever love.