P/E ratio -- The price-to-earnings ratio is the most widely cited valuation metric, and for good reason. It's an easy way to compare similar businesses. Simply divide a company's current share price by its last 12 months' worth of earnings. You can also use the projected earnings over the next 12 months to calculate the forward P/E ratio. The key point to know is that P/E ratios are most useful when comparing businesses in the same industry -- such as comparing ExxonMobil (NYSE:XOM) and Chevron (NYSE:CVX).
Some scammers will buy up a ton of some near-bankrupt, almost lifeless penny stock, then use lies and exaggerations to push the share price much higher. They might say the company is about to get some huge business deal with Google or their neighbor just struck gold in their similar mine, or they are going to land a major FDA clearance. That typically helps increase the value of the penny stock, which creates a profit for the promoter or scam artist. As the shares increase in value, they sell their holdings. These shares usually collapse back down to near-worthless status once the promoter has taken their profits and moved on. 
If investing in single stocks may be too risky for you, consider investing in good growth stock mutual funds. Mutual funds are a simple, even boring, investment plan, yet they work well for most people. Of course, all investing requires a degree of risk; there really is no sure thing. But mutual funds are a great balance of reasonable risk and excellent returns. They have built-in diversification that will keep you from putting all your eggs in one basket.
Buy “the basket”: Can’t decide which of the companies in a particular industry will be the long-term winner? Buy ’em all! Buying a basket of stocks takes the pressure off picking “the one.” Having a stake in all the players that pass muster in your analysis means you won’t miss out if one takes off, and you can use gains from that winner to offset any losses. This strategy will also help you identify which company is “the one” so you can double down on your position if desired.

Dollar-cost average: This sounds complicated, but it’s not. Dollar-cost averaging means investing a set amount of money at regular intervals, such as once per week or month. That set amount buys more shares when the stock price goes down and fewer shares when it rises, but overall, it evens out the average price you pay. Some online brokerage firms let investors set up an automated investing schedule.

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