Buffet has spent 10 of thousands of hours studying company's. He knows his own criteria so well that he doesn't need to write anything down , Let alone do any calculation's or DCF's. The stock price doesn't mean anything about the company's value in Buffet eyes- as he believes markets are "inefficient", and modern finance is wrong. He's said to work out a company's intrinsic value in his head, then he'll take a hefty discount off that price for margin of error. Buffet has giving lots of examples of his investment criteria in his annual letters to shareholders, although Buffet has never exactly described how he picks stocks. After reading both of Buffet's Biography's, and his letters to shareholders- I think the best definition of what buffet does comes for Malcolm Gladwell in a book called "blink", where he describes the term "thin slicing"- where experts in a field can accurately pick outcomes of events with only a second of thought- like an automatic process.
