4 Stock Market 'Truths' That Are Dangerously Wrong

Scoring profits in the stock market isn't just about finding winning investments. It's also about avoiding the little landmines that tend to explode on those gains. And sadly, there are many hurdles that you need to be aware of as you make your investment choices.

Some of these investors' wounds can be self-inflicted. For example, a lot of investors buy stocks when the market has been steadily rising, and they sell their stocks after themarket has had a bad stretch. Yet Warren Buffett and others suggest the opposite tack: Sell stocks when the markets are surging, and load up on them when most others are fleeing.

From hidden costs to specious marketing pitches to an unawareness of the basics of cyclical investing, there are other ways in which investors unwittingly sabotage their own long-term performance. Here are four widely held beliefs about investing -- all of them wrong -- and how you can avoid them.

Myth: Wall Street's "Buy" List Is A Great Buy
Investors who use a full-service broker will occasionally be told of a "can't-miss idea that our analysts really like." Don't you believe it. Many brokers are handed a list of stocks by their managers to unload on clients. These are often stocks that are owned by the brokerage firm -- in large quantities -- and when these firms decide they don't want to hold that stock anymore, they try to pawn them off on unwitting investors. In this case, one's man junk is not another man's treasure.

You can usually spot these unwanted stocks by checking how long they have been slapped with a "Buy" rating. These ratings often get quite stale, and analysts infrequently update their ratings on particular stocks. So it's wise to ask when that analyst started recommending that stock. In fact, these firms are required to show a chart in every report revealing a history of ratings changes. If the analyst boosted the stock up to a "Buy" only recently, at least you can be assured that you're not the last one to get this "hot tip."

Myth: ETFs Are Always Low-Cost
In recent years, investors have been switching from mutual funds to lower-cost exchange-traded funds (ETFs). These alternative investments aren't run by high-priced fund managers and can charge lower expense ratios. But they're not as cheap as you think. A typical ETF has an expense ratio of around 0.5% or 0.6% (which means that they cost $50 for a $10,000 order).

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Yet a number of ETFs have expense ratios that approach 0.8% or 0.9%. And that can spell trouble for anyone owning an ETF for just a few months. Considering that the average stock or fund rises about 5% to 8% per year on average, that works out to be less than 2% per quarter. And if you hold an ETF with a higher-than-average expense ratio for just three to four months, you've already spent a big chunk of your potential profits on these onerous fees.