I saw this last night, and Dana Epp has posted a pointer:
Peter Torr has done it again. He has written an EXCELLENTarticle on writing a practical threat model... getting rid of the cruft of useless theory and applying real-world experience to how to get it done. If you are part of a team that needs a no nonsense approach to threat modeling, you should read his article on "Guerrilla Threat Modelling". Well worth the investment in time.
I agree -- this is excellent! Read it, learn it, and think about how to apply it to your own projects.