Ask HN: Resources for creating a pro forma?

I'm about to start fund-raising for my startup, which means we're going to need some financial projections. (We're pre-revenue.) I know the basics—start with your core assumptions, see how they play out, think of it as a learning exercise, etc.—but I'd like to know more specifics. For instance, how should I go about estimating fundamental numbers like the cost of customer acquisition?<p>I'd really like to see some real examples of startup pro formas. There must be some out there. Has anyone who's gone through the process written a good guide, or a detailed reflection on their experience?<p>I'd also like to know if there are any good alternatives to using Excel. Or is that sacrosanct? Are investors likely to require a spreadsheet in .xls format?