Insiders Are Buying – This one is a no-brainer. The CEO is in as good a position as anybody to know the direction of future profits. If he’s buying like there’s no tomorrow, you have to stop and ask yourself what he knows that you don’t. Ditto if he’s selling.

Not ditto if he’s selling. Lynch states several times in One Up that there are many reasons an insider might sell, like if an unexpected expense came up. He recommends only paying attention to insider buying, because that can only mean one thing: the insider thinks the stock will go up.