To help investors make money in any environment, "Mad Money" host Jim Cramer reflected on his more than 30 years of stock picking to devise five rules to invest by.

Rule No. 1:"Don't dig in your heels when you're wrong"

Rule No. 2:"Price matters"

Rule No. 3:"Don't take your cue from an inferior company"

Rule No. 4:"Don't believe the hype"

Rule No. 5: "Be critical of commentary"

One of the most natural and misleading mistakes, Cramer said, is to assume that people on TV criticizing the market must be telling the truth. Don't fall victim to this. People who dislike the market are not any more honest or less self-interested than those who talk up the market and/or individual stocks.

Investors should be just as skeptical of bears as they are of bulls. But to most people, expressing a critical view of the market and/or an individual stock automatically bolsters the commentators credibility. But Cramer said the people criticizing the market in the media aren't necessarily trying to help you.

When people see a commentator recommending a stock, they automatically assume that person owns it and is promoting it for those reasons. But nobody thinks the commentator criticizing the market is just trying to knock stocks down in order to buy them at a lower price.

The rule of thumb is to always be on your guard and think critically of what you hear the commentators say on TV or read in print, Cramer said.

After all, the bearish commentators aren't any more altruistic or honest than the bullish ones.

Call Cramer: 1-800-743-CNBC

Questions for Cramer?

Questions, comments, suggestions for the Mad Money website? madcap@cnbc.com