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salesforce.com (CRM -1.59%) has been an impressive growth story over the years. In fact, though salesforce.com's shares have barely budged year to date, the company guided to at least 30% revenue growth for the current fiscal year.

When the company reports its fiscal 2015 second-quarter earnings on Aug. 21, investors should keep an eye out for any potential revisions to full-year guidance, operating and free cash flow growth, and operating margin trends.

Expectations for the full year are high
Last quarter, salesforce.com guided to fiscal 2015 revenue of $5.3-$5.34 billion, up from prior guidance of $5.25-$5.30 billion (which in turn had been raised from initial guidance of $5.15-$5.20 billion first issued in the fiscal 2014 third quarter). According to Yahoo! Finance, the sell-side analyst revenue estimates for the full year range from $5.31 billion to $5.38 billion with the average sitting at $5.34 billion -- the high end of management's current guidance.

Given the analyst estimates for the full year, there appear to be expectations that the company could raise its full revenue guidance yet again (or, at the very least, ultimately come in ahead of current expectations). 

Additionally, consensus (again, per Yahoo Finance) for non-GAAP earnings per share for the year appears to be $0.51, which is at the high end of the $0.49-$0.51 guidance that salesforce.com issued last quarter.

The key takeaway, though, is that the bar is set high.

Free cash flow growth important, too
salesforce.com has been growing its revenue base quite nicely, but in the words of Fool analyst Karl Thiel, "Still, as much as we like to complain about the company's lack of GAAP profitability, there's little arguing with its cash generating power."

Thiel continues, "Free cash flow [in fiscal 2015 first quarter] was $413 million, up 80% from a year earlier, meaning that nearly $0.34 of every dollar in sales became cash available for shareholders, acquisitions, and so on."

The Motley Fool's Investing Wiki notes that free cash flow can be calculated by subtracting capital expenditures from cash generated from operations. On salesforce.com's last earnings call, CFO Graham Smith stated that management, "continue[s] to expect [salesforce.com's] full-year operating cash flow to grow in the mid-20s percentage range year over year."

Smith then addressed the company's capital expenditure plans, noting that it "continue[s] to expect [its] full-year CapEx to be in the range of 5% to 7% of revenue."

In other words, investors should keep a close eye on how quickly operating cash flow and capital expenditures are growing relative to management's expectations.

Keep an eye on operating margin
Revenue growth is an important part of the salesforce.com story, but it's also important to keep an eye on the company's operating margin (which The Motley Fool Investing Wiki defines as operating profit divided by revenue). The greater the company's operating margin, the more of its revenue base that it can actually keep as profit. 

On the company's last earnings call, CEO Mark Benioff indicated that non-GAAP operating margin for the year should improve by between 125 and 150 basis points. Investors should keep a close eye on this, particularly as Smith noted that operating margin last quarter was down 80 basis points year over year.