Some exchange traded funds may not offer as much diversification as you think.

Take an ETF that tracks the S&P 500 for example. Over 10% of the market cap is made up of the biggest technology stocks such as Apple (AAPL - Get Report) , Microsoft (MSFT - Get Report) , Alphabet (GOOGL - Get Report) and Facebook (FB - Get Report) .

"I think not enough people spend time to go to the website, look at what that ETF actually holds," said Peter Tchir of TheStreet's Income Seeker. "There is often a discrepancy between what it says it does and what it actually holds. So one, I want to look for something that's truly diversified where it's not two or three names have 25% of it because you're not getting what you want."

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Editors' pick: Originally published Nov. 3.

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