Focus on market segments -- not the market as a whole -- to find opportunities, said Jim Cramer on his "RealMoney" radio show Monday.

If you sat out September because it's historically a "bad" month for the market, you missed the bull markets in oil, minerals, telecom and Google ( GOOG), said Cramer.

And "you missed the easiest money that was made this year."

Cramer advises:

  • Don't make decisions based on the market.
  • Make decisions based on the sector. If the sector is out of favor, ignore it.
  • If the sector is in bull market mode, buy "best of breed" stocks. At times, you can even buy worst of breed if the sector is strong enough.
  • Stealing Stocks

    Lenny "Nails" Dykstra joined Cramer to talk about Petsmart ( PETM), Koor Industries ( KOR), 3M ( MMM) and TC Pipelines ( TCLP).

    Cramer said Petsmart is a "trade that could work" in anticipation of Petsmart's analyst meeting Thursday. Koor is the General Electric of Israel, said Cramer, but he was "less sure" about 3M's prospects because of concerns regarding a lack of catalysts to propel the stock. TC Pipelines is the "safest of the four," said Cramer. "I like that a lot."

    Callers' Questions

  • Southwestern Energy ( SWN): The stock is now "way, way too high," said Cramer, after recommending it recently on his "Mad Money" TV show. "It is too late to buy."

  • Occidental Petroleum ( OXY): "The most undervalued oil company left," said Cramer, adding that he believes that the stock is 15 points undervalued.

    Cramer believes the company will announce a positive earnings surprise soon because its chemical division is able to buy oil feedstock from itself, so it should have a cost advantage vs. competitors. OXY recently traded at $85.45 Monday afternoon.

  • Amylin Pharmaceuticals ( AMLN): Amylin's diabetes drug, Byetta, continues to surprise to the upside, said Cramer. The drug's story has legs, and the stock is not overvalued because prescription data has been "too positive," he said.

  • GameStop ( GME): Cramer said he would be buying it aggressively. He believes that after the Electronics Boutique ( ELBO) acquisition is closed, GameStop will become the place to buy the new Xbox 360, which launches in the third or fourth week of November and will be the "hottest thing in the world."

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