There are two general ways to successful investing:
1) Buying primarily value - understand the business, the people behind it and it's real value. If the asking price is less, buy. The more the gap, the better the investment. Set clear limits and stick with them. Existing value is usually overcharged, so this will be harder to get and require much more capital to buy into. There were much more of those deals available in the past, when the general appetite for investment was less.
2) Buying primarily potential - this one is tricky and more risky. You must understand why businesses fail and test and track accordingly. You must understand and intuitively predict what markets want, how to give it to them and who can give it, on top of previous requirements. You should limit this kind of investment in your portfolio, until you get some relevant experience. Start small and always have a team of domain experts around.