(I think this is my first post on ET. Sheeesh.)
NathanG, there's some great (if ho-hum gee-whiz boring) info in the replies to your post. Read them twice.
FWIW, on my first trade (a teensy one), I made 3 days' take-home pay in 90 minutes. MAN[!] but that was fun. And then I lost it all...