my god, man, I hope that this isn't your source for education regarding margin or anything related to stocks or investing. do a little research, read some books and do some googling. don't be swayed too much by anything you hear here. if munhoi is in usairways just prior to filing of their 3rd BR, munhoi has other more fundamental problems than his/her use of margin.
personally, i wouldn't consider it untill i had established a clear track record of overall success in the market with the basics - just buying and selling common stock. once you honestly and genuinely do that, i'd say start looking into options and or margin and other strategies - although if you really do establish the track record, you'll likely find you don't need to take that risk.
Also, NEVER EVER EVER NEVER EVER answer a margin call.
dont buy on margin I bought on margin on US airways 6 months before they filed for their 3rd BK and I had $1.6 million on margin and came days to loosing my house - in fact I havent learned my lesson - and am closer to loosing my house - even buying options is less risky then buying on margin.
my life has been ruined twice doing this - my friends , family and fiance all lost to this what is akind to gambling - its like being on drugs - once addicted - your life goes down a downhill spiral of epic proportions - its only euphoric when you on the right side of the trade - what appears to be success can turn into an instant nightmare.
I got stuck in US airways where at that time it was very thinly traded and couldnt get out without loosing practically everything.
dont do what I did and continue to do - my life is pure hell right now