Well each company does it a little different, and your final fico score is an average of the three. When I bought my house, my highest was a 760-something and my lowest was a 730-something, so it's not exactly a precise science.

I have the breakdown of what percentage of what category goes in at work, I'll try to post it up later. i.e. 25% of your score is based off payment history, 15% off length of history, etc.