Every quarter, many money managers have to disclose what they've bought and sold, via 13F filings. Their latest moves can shine a bright light on smart stock picks.

Today, let's look at investing giant Bill Ackman, who founded Pershing Square Capital Management in 2003. An investor with roots in real estate, Ackman is an activist, often advocating strongly for big changes at companies in which he has invested heavily. Soon after Ackman invested in the Fortune Brands conglomerate, for example, the company began looking to spin off various divisions -- which it has now done, breaking up into the alcohol-focused Beam and Fortune Brands Home & Security (Nasdaq: FBHS).

Pershing Square's reportable stock portfolio totaled $7.6 billion in value as of June 30, 2012, spread over just a small handful of stocks. Now that's concentration! Its top three holdings make up a whopping 58% of the portfolio's total value. They're Canadian Pacific Railway, Procter & Gamble (NYSE: PG), and General Growth Properties.

Interesting developments
So what does Pershing Square's latest quarterly 13F filing tell us? Here are a few interesting details:

Procter & Gamble is a new and very major holding, and one with a lot of promise, despite having recently delivered underwhelming quarterly earnings and revenue and a disappointing performance in emerging markets. Given Ackman's history of activism, investors are watching to see what changes he pushes for. Some speculate that he might want to see some less profitable business units sold off, and the Duracell and IAMS pet food brands have been mentioned as possible candidates.

Pershing Square reduced its stake in Citigroup (NYSE: C). Some worry about its exposure to Europe's in-crisis economy, while others don't like its $100 billion of toxic mortgages. Meanwhile, it was also recently named as one of 26 companies that paid more to their CEOs than they did in taxes. (For the record, the company says that it paid all it owed.)

Pershing's J. C. Penney (NYSE: JCP) stake was unchanged, but remains a very big one, encompassing about 12% of the portfolio. The company is struggling, though, recently reporting that revenue and earnings are down sharply. Long-term debt is down, but still far outweighs cash, and cash flows from operations have been shrinking. Optimists believe in its turnaround plan, though, as it appeals to younger consumers and employs new technologies.

Finally, Pershing Square unloaded several companies, such as Kraft Foods (NYSE: KFT) and Fortune Brands Home & Security. Kraft is planning to split on October 1, separating its faster-growing snack businesses and slower-growing grocery businesses, and has recently been upgraded by Jeffries, which anticipates that value will be unlocked, with the break-up. The company recently reported estimate-beating results, growing even in troubled Europe.

Fortune Brands Home & Security was in my colleague Jim Royal's "Special Situations" real-money portfolio, but like Ackman, he also sold off his position. The stock has doubled since its debut almost a year ago, leaving it no longer looking like a bargain. Its net income rose 9% in the second quarter, while revenue advanced 5%. The maker of home furnishings such as faucets and locks is poised to profit further as our housing market's recovery gains steam.

We should never blindly copy any investor's moves, no matter how talented the investor. But it can be useful to keep an eye on what smart folks are doing, and 13F forms can be great places to find intriguing candidates for our portfolios.

Procter & Gamble's history of treating shareholders well earned it a coveted spot in our list of the three Dow stocks dividend investors need. To see what other stocks could help you retire rich, just click here and get your copy of our analysts' report.