Charlie Munger (Trades, Portfolio) when discussing how to value a business said that he had never seen Warren Buffett (Trades, Portfolio) break out an excel spreadsheet to determine value.
If an opportunity isn't obviously table pounding attractive, Munger and Buffett aren't interested.
Value investing Professor Aswath Damodaran is a little more scientific in his approach. In the video below he discusses how multiples vary across companies and industries
