I really enjoyed Peter Lynch's books and readily acknowledge his greatness as the Fidelity Magellan manager from 1987-1990.
However, there's one belief/tip he gives investors that I frankly disagree with. Lynch is a huge advocate of individual investors "knowing" the industries in which they invest.
I say no way. When you're buying a share in a corporation, you're making a prediction about future earnings, dividend yields, and your resultant capital gains.
You could know everything in the world about Google (GOOG), but that wouldn't have stopped you from being down around $300/share if you got in at the stock's peak. And you don't have to know squat about Proctor & Gamble (PG) to know that a reliable consumer staples stock with a reasonable P/E ratio and a steady dividend yield makes for a great long-term investment.
I have my portfolio and I don't plan to sell anything for years. I am going to buy, hold, and steadily accumulate more and more shares based on dividends and new share purchases. I'll research my stocks from time to time, yes. But for me (a committed buy-and-hold investor) to think that this research is somehow going to drive stock prices up makes about as much sense in my mind as thinking that if I could just learn more about the Patriots' offensive schemes, they would actually win next year's Super Bowl.
That dog isn't going to hunt.