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 Westfield Capital Management, an investment advisor serving institutions and wealthy investors. It employs deep fundamental research as it seeks out stocks that are underloved by the market, and its funds have outperformed their benchmarks, on average, since inception.

The company's reportable stock portfolio totaled $14.2 billion in value as of September 30, 2012.

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

New holdings include Riverbed Technology (NASDAQ:RVBD.DL) and NetApp (NASDAQ:NTAP). Telecom infrastructure supplier Riverbed has been pressured, in part, by Europe's woes and an overall sluggishness in demand, but it's poised to profit from the growth in cloud computing. My colleague Tim Beyers is a fan of the company, and likes its $1 billion purchase of OPNET Technology (NASDAQ: OPNT), which will boost its monitoring capabilities. Some see Riverbed as an attractive acquisition target.

Data storage specialist NetApp (NASDAQ:NTAP) recently hit a 52-week low, and has also been seen as a buyout target. The company has lost market share to rival EMC (NYSE:EMC), but demand for data storage seems assured for quite a while, and NetApp is promising, generating plenty of free cash flow.

Among holdings in which Westfield increased its stake was Nuance Communications (NASDAQ:NUAN), a specialist in voice recognition technology. It has been benefiting from having components in a variety of popular iDevices (think Siri), and has been diversifying into new areas, such as health care. The company is also not standing still, recently introducing technology that includes biometrics, so that it can identify people by their voice. (This can be a big deal for applications that require security, such as banking.) Bears worry about competition in speech recognition from AT&T (NYSE:T) and others.

Westfield reduced its stake in lots of companies, including Las Vegas Sands (NYSE:LVS). Meanwhile, casino titan Las Vegas Sands has been hurt by sluggishness in Las Vegas, but Vegas-generated casino revenue recently improved, which bodes well for the industry. Many have been bullish on the company's prospects in places such as Macau and Singapore, but Singapore has been a big disappointment lately. Management signaled confidence in the company, though, by recently hiking the dividend by a whopping 40%.

Finally, Westfield unloaded several companies, such as ON Semiconductor (NASDAQ: ONNN). The company has had a tough year, with its stock dropping 21%. Part of the problem was flooding in Thailand, which shut down some of its locations. There are plenty of reasons to steer clear of the stock for the moment, such as the departure of its COO, the downsizing of 250 workers, and the not-yet-so-beneficial acquisition of Sanyo. The company has blamed the global economic slowdown, and has been buying back shares.

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. Therefore, 13-F forms can be great places to find intriguing candidates for our portfolios.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.