Honestly, if you have to ask these questions on a BBS dedicated to an online game, you might want to rethink your ideas about trading. You don't seem to be equipped to do your own research and will likely lose your shirt.
That said, I have used TDAmeritrade with no problems, but I don't do a whole lot of trading. I'm more of a value investor. I look for solid companies with a low multiple to buy into and hold for a period of time.