Sometimes people want to start buying shares, do not make a move and then bore their mates claiming that they almost made a killing. Spotting a good business, though, is not the same as spotting a great investment opportunity — and then acting on it! If I had never invested in the stock market before and wanted to start buying shares, here are five questions I would ask about any potential share purchase I was eyeing. I still use them as an experienced investor. Selling low-priced items to just a few customers is not the way for a business to thrive. A business might not need lots of customers, if the unit price is high enough (Rolls-Royce (LSE: RR) is an example). But I think a business needs a certain financial size of total customer demand to succeed at scale, both now and in the future. A big market is not necessarily a profitable one, though. In fact, the opposite can be true: a large, growing market can attract lots of participants, pushing down selling prices. That is exactly what Tesla and other electric vehicle makers are wrestling with right now. So I look for a competitive advantage that can...