NEW YORK (TheStreet)  -- The world of investing is complicated. If it weren't, there'd be no need for financial advisers, pundits, asset managers and the wide array other specialists who exist to help us navigate Wall Street.

Stanford professor Kathleen Eisenhardt wants to make it simpler, and her new book Simple Rules: How to Survive in a Complex World offers tools for doing just that.

"Simple rules can make it easier for the 40% of Americans who feel overwhelmed by the stock market," she said.

With only two or three things to keep in mind, it's easier to set a plan and stick to it. "If it's a complicated rule book, people won't follow it."

Also a plus for simplicity: "It takes the emotion out [of investing]," she said. If you're following few simple rules, you're less likely to fall prey to the sorts of costly decisions that too many investors make: Selling in a panic, buying into a bubble, etc.

The real question is, which of those few simple rules are right for you? The classic adage, "Buy when there's blood in the streets," she notes, worked for Baron Rothschild -- but he, unlike most investors today, had the knowledge to discern when the proverbial (and non-proverbial) blood really was flowing.

Beyond just hewing to a few simple rules, she said, it's important to have those rules prioritized in case they come into conflict. "You may have some special knowledge ... about the oil industry," she said. "Then you might have a priority that anytime you see a good deal in the oil industry, because you track that industry, you go for it, even if maybe it wasn't your investment goal."

And sometimes, she agrees, you have to throw out the rulebook. And her advice on when to do that, naturally, is simple. "I think the rulebook's gone when it's not working for you. When the market is up, and you're not, it's time to change," she says. Or when your life situation changes; for example, when you're getting closer to retirement.

So, keep just a few rules, but know when to throw them away? Sounds doable.

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.

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