if you've never traded with real money before, my advice would be to open a small account first.....like a 5k margin account with Ameritrade, Etrade, or Scottrade....and just trade some 100 share lots to learn how to place some orders, stops, and get the feel of how executions and routing works....then start trading 12,000+ share blocks.
. It has to be a well known, big broker.