Make sure whoever's advice you buy on this forum, look to see how long they have been here, so you at least get an idea of how long they have been trading so you know if they know what they are talking about. Like if some guy who just registered on elite trader 6 months ago is telling you how he became profitable, dont trust it. If someone who registered in 2002 is telling you, he MIGHT be a bit more credible as he has withstood a good number of years with the market.
Now with that said...the last thing i learned was not to put a large chunk of your cash in 1 trade and NEVER use margin I dont care if your account is 2000 dollars or 2,000,000 dollars. If you feel like you HAVE to use margin, then you dont have the emotional ability to trade. If you cant be patient with your gains, then be prepared to lose it all.
IMO, the ONLY people that can use margin are the guys that have at least 250k in the bank and are trading 25k accounts. These are the guys that make a couple hundred K per year and are pulling cash out when they get their account to 100k or so.
This advice is easy to give, but hard to listen to. Chances are you will be like the rest of us who had to blow our accounts(or blow a substantial amount of money) to find out what works for us or what trains us the best.