Analyst upgrades:

• Goldman upgraded Nokia (NYSE: NOK) to Neutral from Sell on valuation and believes the company's guidance is realistic.
  
• SMH Capital upgraded GMX Resources (NASDAQ: GMXR) to Accumulate from Neutral and is positive on the company's capex reduction.
  
• Wachovia raised Nationwide Health Services (NYSE: NHP) to Outperform from Market Perform to reflect the company's diversified portfolio and "solid" capital position.
• Portugal Telecom (NYSE: PT) was upgraded to Equal Weight from Underweight at Morgan Stanley.
  
• Omnicare (NYSE: OCR) was upgraded to Buy from Hold at Soleil.
  
• SKF AB (OTC: SKFRY) was upgraded at JP Morgan to Neutral from Underweight.

Analyst downgrades:

MOST NOTEWORTHY: Google, Boyd Gaming and Microsoft were today's noteworthy initiations:

• Kaufman Bros. believes Google (NASDAQ: GOOG) has "only begun to scratch the surface" of its local market opportunity. Shares were assumed with a Buy rating and $680 target.
  
• Banc of America believes Boyd Gaming (NYSE: BYD) will face financing challenges with its Echelon resort, and initiated shares with a Sell rating and $14 target.
  
• Lehman reinstated Microsoft (NASDAQ: MSFT) with an Equal Weight rating and $34 target based on peaking Vista/Office 2007 cycles, uncertain online strategy, and increased investment.

OTHER INITIATIONS:

• Goldman started AON Corp. (NYSE: AOC) with a Neutral rating.
  
• Broadpoint initiated Covanta (NYSE: CVA) with a Buy rating and $32 target.
  
• Companhia Vale Do Rio Doce (NYSE: RIO) was assumed at Citigroup with a Buy rating and $48 target.

This is the third in a series of trend-spotting tips from Hilary Kramer's newly-released book, Ahead of the Curve.

Another tip I make use of in my book is this: It pays to think like a detective! The key is to collect clues wherever they are and use them to come to a conclusion about how to solve the crime -- or in this case, to solve the problem of how to make profitable investments.

This tip came into play the other day when I was walking down the street on a garbage day in New York. The bags from an apartment building were piled so high they'd spilled over to block the sidewalk. After navigating this minefield, I got to the subway, on my way out at my stop, I dropped my newspaper in a rubbish bin instead of recycling it -- and noticed that the bin was full of other newspapers that should have been recycled.

MOST NOTEWORTHY: Digital River Inc (DRIV) was today's only notable initiation.

• American Technology initiated Digital River Inc (NASDAQ: DRIV) with a Buy rating and $65 target. The firm believes Q1 guidance could be weak, but feels weakness would be short-lived as investors gain a better understanding of Digital River's Microsoft Corp- (NASDAQ: MSFT) driven revenue and margin upside in the second-half of 2007...

OTHER INITIATIONS:

• Merriman initiated Idera Pharmaceuticals Inc (AMEX: IDP) with a Buy rating and put fair value at $10-$12 a share.

• Merrill Lynch reinstated Nvidia Corp (NASDAQL NVDA) and KLA-Tencor Corp (NASDAQ: KLAC) with Buy ratings.

• Jefferies initiated CommScope Inc (NYSE: CTV) with a Buy rating and $37.50 target; they believe CommScope is a solid play with trends such as increasing competition among cable operators and wireline service providers as well as increasing bandwidth consumption by enterprises.

• Raymond James started Keystone Automotive Inds Inc (NASDAQ: KEYS) with a Market Perform rating.

• Roth Capital initiated G. Willis Food Int'l Ltd (NASDAQ: WILC) with a Buy rating and 48 target; Roth expects the largest marketer and distributor in Israel of kosher food products to grow at a 15%-20% rate over the next several years.

• JP Morgan initiated Covanta Holding Corp (NYSE: CVA) with a Neutral rating on valuation.

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).