For reviews of online brokerages, check these links out:
http://www.google.com/search?num=100...ge&btnG=Search
Choosing the online brokerage, though, is the easy part.
I hope you know what you are doing as far as studying the histories of the stocks, and what it was - historically and economically - that caused the ups and downs of them.
I dabbled in day trading for a few years, but stopped a couple years ago...when I realized how much time it really takes to do it well.