Talk to a stockbroker for investing in individual stocks.
I think the best route personally is mutual funds. There's a whole variety of mutual funds for different industries: including medical, natural resources, computers, security and services as well.
They're very stable and conservative. Over time you can double your money every 5 years I believe. It's called the rule of 72.
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Here and there you can use those earnings on additional stocks in mutual funds or you can diversify or financial portfolio with individual stocks, options and derivatives. The options and derivatives are really risky though and you really have to know some background information or even resort to insider trading which is illegal.