Adding on to what xerxes said; I too have dabbled in margin lending, CFD's. I lost money, and stayed away. I realised that playing the share price is like going to the casino, no one can predict share price movements over the short term.
After that I decided to play the company fundamentals. I bought up shares in spec miners, "falling knives" and I guess what you could generally call "dogs". I made good money but also lost large amounts.
So I stayed away from those too. These days I only play the fundamentals, and only in companies which are top drawer. I figured if I buy a stock like ASX Limited at 8% earnings yield there's no way I can lose money provided I hold the stock forever. If 10 years from now there isn't more trades going on on the stock exchange, I'll eat my hat. The fact that the earnings will at least keep up with inflation due to its ability to hike fees without recourse is just a bonus. These kind of opportunities are rare, but hey, as a wise feller once said "If the price isn't right I don't have to buy the business. I was happy the day before I found out about the offer and I'll be happy the day after" -- I thought about this a bit and realised this is the best attitude yet to take when approaching the market! I have a healthy life, have good relationships with people around me, and have the opportunity to enjoy many of lifes pleasures. If you focus on what you have, rather than what you don't have, it's much harder to fall into the trap of taking risky positions on the stock market.