Legendary money manager Ken Fisher outlines the most common—and costly—mistakes investors make.

• Small cap stocks are best for all time. Bunk!
• A trade deficit is bad for markets. Bunk!
• Stocks can't rise on high unemployment. Bunk!

Many investors think they are safest following widely accepted Wall Street wisdom—but much of Wall Street wisdom isn't so wise. In fact, it can be costly bunk.

In Debunkery: Learn It, Do It, and Profit From It—Seeing Through Wall Street's Money-Killing Myths, Ken Fisher—named one of the 30 most influential individuals of the last three decades by Investment Advisor magazine—details why so many investors fail to get the long-term results they desire. The short answer is many investors fail to question if what they believe is true—and are therefore blinded by tradition, biases, ideology, or any number of cognitive errors.

Your goal as an investor shouldn't be to be error-free—that's impossible. Rather, to be more successful, you should aim to lower your error rate. Debunkery gets you started by debunking 50 common myths—but that's just the beginning. It also gives you the tools you need to continue to do your own debunkery for the rest of your investing career.

KEN FISHER is best known for his prestigious "Portfolio Strategy" column in Forbes magazine, where his over 25-year tenure of high-profile calls makes him the fourth longest-running columnist in Forbes's 90-plus year history. He is the founder, Chairman, and CEO of Fisher Investments, an independent global money management firm with over $32 billion under management (as of 6/30/10). Fisher is ranked #289 on the 2009 Forbes 400 list of richest Americans, and #721 on the 2010 Forbes Global Billionaire list. In 2010, Investment Advisor magazine named him as one of the 30 most influential individuals of the last three decades. Fisher has authored numerous professional and scholarly articles, including the award-winning article, "Cognitive Biases in Market Forecasting," and has published six previous books, including the New York Times and the Wall Street Journal bestsellers, The Only Three Questions That Count, The Ten Roads to Riches, and How to Smell a Rat, all of which are published by Wiley. Fisher has been published, interviewed, and/or written about in many major American, British, and German finance or business periodicals. He has a weekly column in Focus Money, Germany's leading weekly finance and business magazine.

LARA HOFFMANS is a content manager at Fisher Investments, a contributing editor of MarketMinder.com, and coauthor of the bestsellers, The Only Three Questions That Count, The Ten Roads to Riches, and How to Smell a Rat.